Intertidal Species of Andamanwhat lives between the tides

How to recognise it

• A rounded, flat shell with green and white stripes running across it.
• Many fine slanting lines on the sides of the shell.
• The tips of the claws are shaped like small spoons.
• Usually seen in a group on rocks above the water line.

Where to find it

Bare rocks hit by waves at the very top of the shore, and the tops of reefs where the waves break. It spends most of its time out of the water. On Neil there are photos of it on the rocks at Lakshmanpur.

How it lives

It eats mostly algae from the wet rock, and some animal food as well. SeaLifeBase calls it a key species of healthy, exposed rocky shores.

Easy to confuse with

• Other shore crabs (Metopograpsus): They lack the bold green-and-white stripes.

How to recognise it

• Bright red eyes on pale stalks.
• A rounded shell with small bumps and small teeth along the front edge, brown to dark grey or purple.
• Smooth claws of unequal size. The big one has heavy, molar-like teeth.
• Hairy walking legs.

Where to find it

Wedged into cracks and holes in rock, under stones and in coral rubble, from the middle of the shore down into shallow water. You mostly see the eyes and the tip of a claw.

How it lives

It feeds at night and hides by day, wedging itself into a crack so tightly that it is very hard to pull out. The big claw cracks snail shells. It is known to be aggressive, so keep your fingers out of its hole.

Easy to confuse with

• Pimply Red-eyed Crab (Eriphia smithii): Its big claws are covered in small bumps. This one has smooth claws.

How to recognise it

• A flat, clam-like shell of thick white plates on a leathery stalk.
• Fine grooves run across the plates.
• The stalk is orange.
• Grows in clusters on driftwood and floating rubbish.

Where to find it

Walk the drift line, the line of seaweed and rubbish left by the last high tide, especially after rough weather. Look on logs, coconuts, rope and plastic. Stranded goose barnacles usually die.

How it lives

It sweeps the water with feathery legs to catch plankton. It cannot move on its own once it settles, so it goes wherever its raft drifts, across whole oceans.

Easy to confuse with

• Common Goose Barnacle (Lepas anatifera): Smoother plates and a dark purplish-brown stalk. To be sure you need a microscope, so photos of goose barnacles are often hard to name.

How to recognise it

• A box-shaped body, sandy or bluish grey with brown markings, often in an H shape.
• Adults have a tall thin horn on top of each eye. Young crabs have no horns.
• Long pointed legs. Pale claws, one bigger than the other.
• Large burrow holes with a spray of sand, high on the beach.

Where to find it

Sandy beaches all around the islands, in deep burrows near or above the high-tide mark. Walk a beach after sunset with a torch to see them running.

How it lives

It eats dead fish, shrimps and worms washed up by the tide, and hunts small clams and snails at the water's edge. Its burrows go deep, so please do not dig them up.

Easy to confuse with

• Smooth-eyed Ghost Crab (Ocypode cordimanus): No horns on the eyes. Remember that young Horn-eyed Ghost Crabs have no horns either.

How to recognise it

• Males have one huge smooth claw, almost twice as long as the body is wide, pink to nearly white.
• Females have two small claws.
• A small squarish body, dark to pale, with dark, blue or white stripes. Eyes on long stalks.
• Walking legs from dark to orange, brown or reddish.

Where to find it

Sandy or silty flats near the low-tide mark, often next to mangroves, each crab beside its own burrow.

How it lives

They live in big groups and vanish into their burrows at a footstep or a shadow, so stand still and wait. They scoop up mud and sand and eat the thin film of food on the grains. At high tide each crab hides in its burrow and plugs the door with sand.

Easy to confuse with

• Tetragonal Fiddler Crab (Gelasimus tetragonon): Usually blue or turquoise. Photographed on the sand and rubble flats of Havelock beaches, such as Beach No. 5.
• Other Austruca fiddler crabs: Very alike. They are told apart by small details of the big claw, not by colour.

How to recognise it

• Lives in an empty snail shell and is seen on land, not in the water.
• Left claw usually bigger than the right. Brownish, pale or dark purple.
• A row of slanting ridges on the outer side of the left claw (you need a close look).
• Eyes on short, flattened stalks.

Where to find it

Above the high-tide line: on the upper beach, along the drift line among rubbish and rocks, and under the trees and grass behind the beach. Most active at night.

How it lives

It scavenges rotting leaves, fallen flowers of beach plants and dead animals. Big empty shells are scarce this high up the shore, so many crabs live in shells that are too small for them. They can be very common: one study in Phuket counted about seven per square metre.

Easy to confuse with

• Other land hermit crabs (Coenobita brevimanus, C. violascens): No row of slanting ridges on the left claw. Most visitors can simply call them land hermit crabs.
• Left-handed Hermit Crab: Lives in tide pools, in the water, not on dry sand.

The law

Please do not take hermit crabs or their shells home. Empty shells on the beach are the homes they move into next.

How to recognise it

• Left claw much bigger than the right.
• Claws dark purplish-brown to black with white tips.
• Eyestalks blue at the base and orange at the tip.
• Walking legs brown with white bands at the tips.

Where to find it

In tide pools and on reef flats, rock platforms and coral rubble, from the low shore into shallow water.

How it lives

It prefers round snail shells such as nerites and turban shells. It is a fighter and will battle other hermit crabs for a better shell.

Easy to confuse with

• Clibanarius hermit crabs: Their two claws are about the same size.
• Land Hermit Crab: Lives on dry sand above the tide, not in pools.

How to recognise it

• Looks like a big shrimp with stalked eyes that swivel.
• Males dark green to brown. Females grey-green to whitish.
• The folded front limbs end in a heavy club, used for smashing, not spearing.

Where to find it

On reef flats and tidal flats, hiding under rocks and boulders or in holes in coral and rock, from the upper shore into shallow water. Turn rocks carefully and put them back the same way.

How it lives

It hunts in the day, moving between coral heads, and breaks open snails, hermit crabs and clams with blows of its club. It lives in a hole that it trims to fit, and often blocks the entrance with sand and stones at night.

Easy to confuse with

• Other Gonodactylus mantis shrimps: Two more species are recorded in South Andaman. They differ in small markings and are hard to tell apart on the shore.

How to recognise it

• The last pair of legs is flattened into paddles for swimming.
• Five spines of about equal size along each side of the front of the shell.
• Six small rounded lobes between the wide-apart eyes.
• Claws powder blue with dark red tips. Body sandy, olive or pinkish.

Where to find it

In shallow water at low tide on sandy-muddy flats, near seagrass and reefs, and around mangroves.

How it lives

A hunter and scavenger. It feeds on slow-moving animals around the mangroves and also eats dead animals.

Easy to confuse with

• Other swimming crabs (Thranita, Thalamita): Told apart by the number and size of the side spines and the lobes between the eyes.

How to recognise it

• A thick, cone-shaped shell like a small volcano, greenish grey.
• The shell has ridges or short lines and does not look like separate plates.
• A small opening at the top, with a "door" set deep inside.
• Fixed firmly to rock, often in groups.

Where to find it

On rocky shores, on big boulders and steep rock faces that get plenty of waves, often in places shaded at low tide.

How it lives

When the tide covers it, it opens its door and sweeps the water with feathery feet to catch plankton. At low tide it shuts the door to stay moist, and its thick, air-filled shell keeps out the heat.

Easy to confuse with

• Small acorn barnacles (Chthamalus): Much smaller, higher on the shore, and the shell clearly shows separate plates.

The law

Wear shoes on rocky shores. Barnacle and coral cuts often get infected and can take weeks to heal.

How to recognise it

• A heavy, cone-shaped shell with a sharp shoulder and an almost flat top.
• White, with spiral rows of square to round blackish-brown spots from the shoulder to the base.
• Usually three yellow-orange bands around the shell, which can be faint.
• A live shell is covered in a brown skin that can hide the pattern.

Where to find it

On sheltered shores with mud, gravel and seagrass, in the middle and lower shore, never high up, usually partly buried. Elsewhere it lives from just below low tide down to about 50 m.

How it lives

It eats only marine worms, which it kills with venom. A bigger cone, the Marbled Cone, eats it in turn.

Easy to confuse with

• Leopard Cone (Conus leopardus): A very close relative that often lives in the same places. It differs in its bands and number of spots, and even experts check carefully.
• Hebrew Cone (Conus ebraeus): Much smaller, white with bold black blocks. It is the most common cone on South Andaman shores, more than half of all cones counted in the Port Blair survey.

How to recognise it

• Usually all you see is a wavy, fleshy mantle between two shell edges, set flush into a coral boulder.
• The mantle colour varies: often bright blue, turquoise or green with dark patches, sometimes brown.
• Small: rarely longer than a hand.
• A greyish-white shell with low ribs, often edged orange or yellow.

Where to find it

Sunk deep into living or dead coral boulders in shallow water near living reefs. On the Thai side of the Andaman Sea it was found from the shore down to 7 m, more on the reef flat than on the slope.

How it lives

It can also filter food from the water, but most of its food comes from those algae. It turns its open shell towards the light, and clear lens-like spots in the mantle focus light onto them.

Easy to confuse with

• Small Giant Clam (Tridacna maxima): Grows much bigger, up to about 40 cm, and sits only partly sunk into the reef, so more of its ridged shell shows. Schedule I protected.
• Fluted Giant Clam (Tridacna squamosa): Up to about 45 cm, sits loose on the reef, with big frilly scales on the shell. Schedule I protected.

The law

This species is not named in India's Schedule I, but two of its look-alikes are, and every giant clam is in Appendix II of CITES, which controls international trade. It cannot trap a hand or a foot; the danger is to the clam, from trampling and collecting.

How to recognise it

• A flat oval with a row of eight overlapping shell plates down the back.
• Plates usually worn and brown to dark brown.
• A wide fleshy rim round the plates, covered in short, thick spines, like a velvety border.
• Clamps flat and tight to the rock.

Where to find it

On rock and beachrock between the tides, up to the high-tide mark. By day it sits in a shallow dip it has scraped into the rock, so look on bare rock and in cracks.

How it lives

It grazes thin algae off the rock with a rasping tongue, feeding at night low tide. When two chitons turn up at the same home they push and fight over it. The home also protects it from a pufferfish that eats chitons.

Easy to confuse with

• Limpets: A limpet has a single cap-shaped shell. A chiton has eight separate plates in a row.
• Other chitons: Smaller chitons also live on Andaman rocks. This is the big one with the thick, furry rim.

How to recognise it

• A firm, warty slug with no frilly gills on the back.
• A blue to blue-grey back with black bands; the blue ridges form a Y shape.
• Separate yellow-capped bumps down the middle that never join into a ridge.
• A broad, bumpy blue-grey edge and a plain grey underside.

Where to find it

On reefs and rubble from about 1 m down, so look while snorkelling.

How it lives

It eats sponges. It takes in the sponges' toxic chemicals and uses them for its own defence. When disturbed it gives off a milky slime, and its bright colours probably warn predators away.

Easy to confuse with

• Varicose Phyllidia (Phyllidia varicosa): Bigger, with three to six long, bumpy blue-grey ridges topped with yellow bumps, and a black stripe underneath.
• Ocellate Phyllidia: Yellow-orange with black rings, not blue.

How to recognise it

• A hard, warty slug, yellow to orange.
• Four to ten black rings edged with white on the back, each with a gold or white bump in the centre.
• The pattern varies a lot: the black can spread, and some lack the white.
• Yellow feelers at the front and no frilly gills on the back.

Where to find it

On coral rubble and reefs, mostly below the low-tide line.

How it lives

It moves about in the open and feeds on sponges. When disturbed, bad-tasting chemicals ooze from its bumps, taken from the sponges it eats.

Easy to confuse with

• Phyllidia flava: Also golden yellow, but with no black at all.
• Sky Blue Phyllidia: Blue-grey with black bands, not yellow.

How to recognise it

• A broad, flat oval body with a thin fin all round the edge.
• Males especially show bold "tiger stripes" across the back and head.
• A narrow, pale, broken line along the base of the fins.
• Changes colour in a moment. W-shaped pupils, eight arms and two long feeding tentacles.

Where to find it

From the shoreline down to about 110 m, most common in the top 40 m, over sand and seagrass. Adults gather in groups to spawn in water no deeper than about 20 m.

How it lives

An active hunter of shrimps, crabs and small bottom fish. Around India it spawns almost all year. It lives about 2-3 years, and adults usually die soon after spawning.

Easy to confuse with

• Broadclub Cuttlefish (Sepia latimanus): A reef cuttlefish seen over coral rather than open sand and seagrass, without tiger stripes. Cuttlefish are hard to name from a quick look.

How to recognise it

• A small, squat, almost six-sided shell. Shells on the shore are usually smooth; ones from deeper water often have knobs at the sides.
• Yellowish white to bright yellow, with dark smudges round the humped middle.
• A plain white underside with white "teeth" along the slit-like opening.
• When it is active, a thin see-through skin (the mantle) with fine dark bars covers the shell.

Where to find it

On reef flats and rocky shores between the tides, in cracks, under rocks and in pools.

How it lives

Like most cowries it hides by day and comes out at night to graze small seaweeds. Money cowries follow each other's slime trails, and in one study most were found in male-female pairs. When disturbed it pulls its mantle back inside the shell.

Easy to confuse with

• Ring Cowrie (Monetaria annulus): Similar size, but grey-white to bluish with a clear golden-orange ring on the back.
• Tiger Cowrie: Much bigger and covered in dark round spots.

How to recognise it

• A large, glossy, egg-shaped shell.
• White, cream or bluish-grey, densely covered in round dark brown to black spots.
• A white underside and white "teeth".
• The living animal often covers the shell with a mantle patterned with dark lines and small finger-like "hairs".

Where to find it

Near living reefs, often on live coral, and also in seagrass and on sand and rubble. Where it has been heavily collected it may survive only below about 10 m.

How it lives

Unusually for a cowrie, it is active by day. When disturbed it pulls its mantle back and the shiny shell shows.

Easy to confuse with

• Mole Cowrie (Talparia talpa): A long shell with brown bands and no spots. It is protected in Schedule II.
• Money Cowrie: Much smaller, yellowish and knobby, with no spots.

The law

Tiger cowries are heavily collected for the shell trade in other countries, and where that has happened they survive only in deeper water. Please leave every shell where it is.

How to recognise it

• A thick, almost round shell like half a marble, with the top hardly sticking out.
• Smooth and often glossy, with no ribs.
• Colour and pattern vary a lot: white, cream, brown, grey or greenish, marbled or streaked.
• A flat, glossy white underside with small notched "teeth" at the opening, and a thick greenish-grey door.

Where to find it

On rocky shores, often near the high-water mark. By day it lies shallowly buried in sand against the foot of rocks.

How it lives

It grazes algae off the rocks at night. When the tide is out it seals itself in with a thick door, which keeps it from drying out and stops crabs getting in.

Easy to confuse with

• Ox-tongue Nerite (Nerita albicilla): A flatter, oval shell, with big rounded bumps underneath like an ox's tongue. Lives lower on the shore.
• Waved Nerite (Nerita undata): The top sticks out and the shell has narrow spiral ribs.

How to recognise it

• A big, heavy shell with a wide, flared lip carrying six long, finger-like spines (adults only).
• The top is usually dull and covered in algae, so it looks like a rock.
• The inside of the opening is glossy pink with orange or yellow tints.
• Two large eyes on stalks peep out from a notch at the front.

Where to find it

On reef flats, coral rubble, sand and seagrass near reefs, from the low-tide mark down to about 5 m. Often half buried and so well hidden that people walk right past it.

How it lives

It does not creep like most snails. It digs its claw-like door into the sand and pushes off, so it moves in hops. The spiny lip keeps it from tipping over, and if it is turned over it rights itself with that same door. It mainly grazes fine red algae.

Easy to confuse with

• Chiragra Spider Conch (Harpago chiragra): Bigger, with six long spines that curve strongly. Protected in Schedule II.
• Scorpion and Millipede Spider Conches (Lambis scorpius, L. millepeda): Knobbly or more numerous spines. Both protected in Schedule II.

The law

This species is not in the schedules, but six of its look-alike spider conches are protected in Schedule II, and it is hard to tell them apart. Leave every conch where you found it.

How to recognise it

• A big, soft, lumpy slug, mottled brown and green, covered in short spikes.
• The back end is cut off flat into a sloping round disc, with an opening in the middle.
• A small head with short, frilly feelers.
• Squirts ink when disturbed.

Where to find it

In intertidal seagrass beds and on mixed shores, in sheltered lagoons, large rock pools and among seaweed.

How it lives

It eats seagrass and brown, red and green seaweeds. When poked it squirts a cloud of purple ink to confuse attackers. Like other sea hares it takes up chemicals from the algae it eats.

Easy to confuse with

• Other sea hares (Aplysia): Smoother, with two wing-like flaps on the back and no flat "chopped-off" rear end.
• Black Sea Cucumber: A sea cucumber has a ring of tentacles at the mouth end and no feelers or ink.

How to recognise it

• A medium to large octopus, usually seen in daytime at or near a hole in the reef.
• Skin that keeps changing colour and texture: brown, reddish or mottled, smooth or bumpy, often with raised points over the eyes.
• Eight arms with suckers, and no shell.

Where to find it

In dens in coral rock, coral heads and holes dug in sand and rubble, on reef flats and in shallow water. In Madagascar and Comoros people catch it mostly on rocky reef flats at low tide.

How it lives

It hunts in daylight, most of all at dawn and dusk. It pounces on crabs, or spreads the web between its arms over a coral head and feels inside with its arm tips for prey. While hunting it changes its skin pattern about three times a minute, to blend in or sometimes to look like something else.

Easy to confuse with

• Blue-ringed octopuses (Hapalochlaena): Small, a few centimetres, with bright blue rings when alarmed, and deadly venomous. One was photographed in the Nicobar Islands in 2025, so never touch any small octopus.

How to recognise it

• A big, heavy, tall cone-shaped shell, the largest horn snail of Indo-Pacific mangroves.
• Often seen in groups on mangrove mud or among fallen leaves.
• Young snails are smaller and live out on the open mud.

Where to find it

On the mud in mangrove forests and on nearby mudflats. Big adults live mostly inside the mangrove among the fallen leaves; young ones are more common out on the open mud.

How it lives

Adults mainly eat fallen mangrove leaves. Young ones eat the thin film of tiny algae on the mud and switch to leaves when the shell is about 5 cm long. They can be very common and churn up the surface of the mud.

Easy to confuse with

• Telescope Snail (Telescopium telescopium): Also big and found on Andaman mangrove mud, but its shell is a broad, flat-based cone, like a telescope.

The law

Mangrove creeks are home to saltwater crocodiles. Look from the edge, stay out of creeks and obey any warning boards.

How to recognise it

• A long, soft, sausage-shaped body, narrower at the front.
• Plain very dark brown to black, with no spots or markings.
• Short soft points and tube feet all over. A ring of 20 dark, bushy tentacles around the mouth.
• Often only the front end shows, sticking out from under a rock.

Where to find it

On reef flats, in pools and in seagrass at low tide. It usually keeps most of its body under a rock or in a crack to stop drying out.

How it lives

It swallows sand and mud and digests the bits of food in it, dabbing the surface around it with its tentacles. When it is bothered it can shoot out thin, sticky white threads from its rear end. These tangle up an attacker. They cling to skin too, but they are not known to harm people.

Easy to confuse with

• Lollyfish (Holothuria atra): Shorter and fatter, usually lies out in the open dusted with sand, and does not shoot white threads.
• Snake Sea Cucumber: Much longer and thinner, brown with stripes and patches, and sticky to touch.

The law

All sea cucumbers are in Schedule I of the Wild Life (Protection) Act, the highest level of protection in India, the same as tigers. Collecting, keeping or selling one is an offence. Look, take photos, and leave it where it is.

How to recognise it

• Black spines, thick and strong with a fairly sharp tip, sometimes with a blue-green sheen.
• The spines feel rough, like sandpaper.
• Five grey zig-zag lines on top of the body where the spines part.
• Usually sits in a hollow or crack in the rock, often with many others.

Where to find it

Rocky shores near the low-tide mark: in rock pools, cracks and gullies, often packed together on rock that the waves hit.

How it lives

It grazes seaweed off the rock, mostly at night. Using its spines and teeth it slowly wears a hollow into the rock to hide in. On wave-beaten shores they can cover a pool like a black carpet.

Easy to confuse with

• Burrowing Urchin: Smaller, usually green, purple, brown or reddish (dark ones can look almost black), with a pale ring at the base of each spine.
• Long-spined Sea Urchin: Much longer, needle-thin spines, an orange ring on top and five white dots.

How to recognise it

• A small round disc with five long, thin, snake-like arms lined with short spines.
• Dark brown to black, often with faint light bands on the arms.
• Usually only the arms show, waving out from under a rock or out of a crack.
• Moves fast by wriggling its arms, unlike a sea star.

Where to find it

In cracks and under stones and coral rubble on rocky and reef-flat shores between the tides.

How it lives

It hides by day. As the rising tide first covers the reef flat, crowds of them lift a few arms and sweep the surface of the water for a minute or two, catching floating food on sticky spines. Then they switch to filtering food from the water.

Easy to confuse with

• Banded brittle star (Ophiomastix annulosa): Also found in the Andamans. Arms more boldly ringed light and dark.

How to recognise it

• Bright blue, sometimes light blue, aqua, purple or orange.
• Five long, smooth, tube-like arms with rounded tips and a small centre.
• Stiff-looking, not soft or floppy.
• Arms often of different lengths when one is growing back.

Where to find it

On rock, dead coral and rubble in shallow, sunny reef areas, from the low-tide line down. Young ones hide under rocks and coral.

How it lives

It moves slowly, about 8 cm a minute, and feeds on the thin film of bacteria, algae and tiny animals on hard surfaces. It can drop an arm to escape a predator and grow it back, so many wild ones have arms of different lengths.

Easy to confuse with

• Other Linckia sea stars: Same shape but brown, pink or mottled red, never bright blue.

The law

Please leave sea stars in the water. Look and take photos without lifting them out.

How to recognise it

• A puffed-up, five-sided cushion with almost no arms.
• Leathery top with small cone-shaped spines.
• Grey, brown, orange or red, often with dark spots.
• Flat underside with grooves of tube feet.

Where to find it

Lagoons and inner reef flats with seagrass and algae, mostly from about 3 m down, so a snorkelling animal more than a low-tide one.

How it lives

A slow grazer that turns its stomach out over its food: the film on algae and seagrass, sponges and the living tissue of corals.

Easy to confuse with

• Pacific cushion star (Culcita novaeguineae): Almost impossible to tell apart by eye. Some Indian survey lists use this name for the Andaman animal.

How to recognise it

• A black ball with very long, thin, needle-like spines (black, banded or white).
• A bright orange ring around the bulb on top.
• Five white dots on the body and lines of small blue dots.
• It swings its spines towards anything that comes close.

Where to find it

At the very bottom of the shore and just below it: in coral rubble, near boulders and in seagrass, often in groups in calm water.

How it lives

It hides in cracks by day and comes out at night to graze algae off dead coral and rubble. Small fish and shrimps shelter among its spines.

Easy to confuse with

• Diadema savignyi: Blue lines instead of five white dots, and usually no orange ring.
• Black Sea Urchin: Much shorter, thicker spines, and lives packed into rock hollows.

How to recognise it

• Medium-length, fairly thick spines in green, purple, brown or red.
• A pale ring at the base of each spine.
• Usually tucked into a hole or groove in rock, not sitting in the open.

Where to find it

In holes and grooves it has dug into rock and dead coral on the reef flat and in shallow water.

How it lives

It stays inside its burrow by day and comes out at night to scrape algae off the rock.

Easy to confuse with

• Black Sea Urchin: Bigger, with truly black, thicker spines and no pale ring at the base.

How to recognise it

• A very long, thin, snake-like body.
• Yellowish brown with darker wide stripes and dark patches.
• 15 feathery tentacles around the mouth, always moving.
• No tube feet. The skin feels sticky and clings to fingers.

Where to find it

On sand and in seagrass beds, or under rocks on reef flats, from the low-tide line down to about 20 m.

How it lives

It crawls slowly over sand and seagrass, dabbing up food with its feathery tentacles. If something grabs it, it can break off pieces of its rear end to escape, and its thin body wall tears easily.

Easy to confuse with

• Black Sea Cucumber: Plain black, much fatter and shorter, and not sticky.

The law

All sea cucumbers are in Schedule I of the Wild Life (Protection) Act, the highest level of protection in India, the same as tigers. Collecting, keeping or selling one is an offence. Look, take photos, and leave it where it is.

How to recognise it

• Two spiral, Christmas-tree-shaped crowns of feathery tentacles sticking out of coral.
• Many colours: blue, yellow, orange, red, white.
• A small hard lid with spikes between the crowns.
• Pulls back into its tube in a flash when disturbed.

Where to find it

In hard tubes buried in living coral heads, especially big boulder corals like Porites. Mostly from about 3 m down, so look while snorkelling off the reef edge.

How it lives

It builds a hard, chalky tube in living coral so that only the crowns show, and uses them to catch tiny food from the water. When disturbed it pulls back and seals the tube with its lid.

Easy to confuse with

• Fan worms (Sabellidae): A single flat or cup-shaped fan, a soft tube and no hard lid. These are the fan worms more often seen at low tide.

How to recognise it

• A long, slim body and a blunt, rounded head with the eyes set high.
• A long fin running most of the length of the back.
• Brown, grey or greenish with darker bands, spots or thin lines. Males of some species have a crest on the head.
• Often seen out of the water on wet rock, or skipping from pool to pool.

Where to find it

In rock pools and on wet rocks of the upper and middle shore, on rocky reef flats, around jetties and breakwaters, and in mangroves. Specimens were collected at Port Blair in the 1930s.

How it lives

It grazes algae off the rock and hides in cracks when it is not feeding. Out of the water it rests under rocks or seaweed. When chased it leaps out and skips to the next pool.

Easy to confuse with

• Barred Mudskipper: Lives on mud in mangroves, has bulging eyes on top of the head and walks on its front fins.
• Other blennies (Entomacrodus): Very similar. You usually need a close photo of the head and fins.

How to recognise it

• A flat, oval fish lying on one side on the sand, with both eyes on the upper side.
• Sandy to brown, covered in pale rings and eye-spots.
• Fins run all round the edge of the body. It often lies half-buried.

Where to find it

On sand and mud in lagoons and around reefs, from about 2 m down to 40 m. You are most likely to see one while snorkelling over sand.

How it lives

It rests buried in the sand by day and feeds on small bottom animals, mostly crustaceans.

Easy to confuse with

• Moses Sole (Pardachirus marmoratus): A close relative from the Red Sea and western Indian Ocean. The Peacock Sole is the one found from Sri Lanka eastward.
• Other flatfishes: Most lack the many pale rings and eye-spots.

How to recognise it

• Long, feathery fins at the sides, spread like wings.
• Tall, separate spines along the back.
• A red-brown to tan or grey body with many thin dark stripes running up and down.
• Small dark spots on the soft back fin, the fin under the tail end (anal fin) and the tail.

Where to find it

On reefs from the surface down to about 85 m. Seen while snorkelling, under jetties and around rocks just past the low-tide line.

How it lives

It feeds mainly on small fish, plus shrimps and crabs. Smaller lionfish eat more shrimps and crabs.

Easy to confuse with

• Red Lionfish (Pterois volitans): Almost the same. It replaces this species east of Sumatra, so it is not expected in the Andamans.

How to recognise it

• A round puffer shape with short spines all over the body.
• Several large dark blotches edged in pale yellow or white, including one below the eye.
• Big eyes. It can blow itself up into a spiny ball.

Where to find it

Adults live on reef edges and slopes and hide in caves and under ledges by day. Young ones are found in lagoons. Seen while snorkelling, from about 1 m down.

How it lives

It lives alone, hides by day and comes out at night to crush crabs and shellfish with its beak-like teeth. Young ones grow up in calm lagoons and estuaries before moving out to the reef edge.

Easy to confuse with

• Spot-fin Porcupinefish (Diodon hystrix): Covered in small black spots instead of a few big pale-edged blotches, with longer spines.
• Pufferfishes (Arothron): No spines on the skin.

The law

Do not eat porcupinefish. This species has caused ciguatera poisoning, and a close relative has caused fatal poisoning when eaten.

How to recognise it

• A small puffer with a pointed snout.
• Brown body with many small white spots on the snout, sides and tail.
• Bluish-white lines around the eye and on the upper back.
• A white-edged black spot below the back fin, and a white belly.

Where to find it

On shallow reefs from about 1 m to 25 m. Seen while snorkelling off the beaches.

How it lives

It is usually seen alone or in pairs on shallow reefs.

Easy to confuse with

• Spotted Toby (Canthigaster solandri): A very similar Pacific species, not recorded from the Andamans.
• Valentin's Sharpnose Puffer (Canthigaster valentini): White with four dark saddles across the back.

How to recognise it

• Bulging eyes set high on top of the head.
• Props itself up and "walks" over wet mud on its front fins.
• Grey-brown body. The first back fin has a black stripe near the edge with small white spots behind it.

Where to find it

On wet mudflats in mangroves, and on muddy shores where it moves in and out of shallow pools.

How it lives

It breathes air and eats worms, crustaceans and insects. Each fish keeps to its own patch of shore and finds its way back to it.

Easy to confuse with

• Boddart's Blue-spotted Mudskipper (Boleophthalmus boddarti): Bright blue spots on the body and fins. It grazes algae on open mud and is recorded around Port Blair.
• Rockskippers: Live on rock, not mud, and have a blunt head without raised eyes.

How to recognise it

• Looks like a lumpy rock covered in algae.
• A large mouth that points upward, and small eyes on top of the head.
• Warty skin in brown, grey, red or orange that matches its surroundings.

Where to find it

On sand and rubble on reef flats and in shallow lagoons, and in small pools at low tide, from the surface down to about 30 m.

How it lives

It lives alone and hardly moves, relying on its camouflage, and ambushes fish and crustaceans that come close.

Easy to confuse with

• Scorpionfishes (Scorpaenopsis): Also camouflaged and venomous, but more fish-shaped, with visible fins.
• Devil Scorpionfish (Inimicus): Buries in sand and flashes brightly coloured fins when disturbed.

The law

First aid (Divers Alert Network): get the person out of the water, soak the stung part in hot water they can bear without scalding (test it on your own skin first), and go to hospital at once. Heat may not ease a stonefish sting much. An antivenom exists, but it is made in Australia and hospitals in the islands may not stock it, so do not wait for it: hot water and getting to a doctor quickly matter most.

How to recognise it

• An oval, yellowish-tan to greenish disc covered in large bright blue spots.
• Blue stripes along each side of the fairly thick tail.
• A venomous spine on the tail.

Where to find it

Around coral reefs, down to about 20 m. It feeds on shallow sand when the tide is in and shelters under reef ledges when it is out.

How it lives

It digs snails, worms, shrimps and crabs out of the sand. It seldom buries itself, unlike many stingrays.

Easy to confuse with

• Blotched Fantail Ray (Taeniurops meyeni): Much bigger, grey with black mottling and no bright blue spots.
• Blue-spotted Maskray (Neotrygon): A dark "mask" across the eyes and smaller blue spots on a reddish disc.

How to recognise it

• A small grey-brown shark with a short, rounded snout.
• A black tip on the first back fin and on the lower tail.
• Yellow-brown above and white below, with a dark band along the flank towards the belly fins.

Where to find it

Close inshore on coral reefs and reef flats, and in mangroves, moving in and out with the tide.

How it lives

It hunts fish, crabs, squid and octopus, alone or in small groups. It is shy and usually swims away, but FishBase notes it can turn aggressive towards spearfishers and has bitten people wading in shallow water.

Easy to confuse with

• Whitetip Reef Shark (Triaenodon obesus): White, not black, tips on the back fin and tail.

How to recognise it

• An eel shape with no scales.
• White to cream body with large black, star-like blotches holding yellow spots.
• Yellow tips to the nostrils. Often only the head shows from a hole.

Where to find it

Between rocks and corals on reef flats, and in shallow lagoons and reefs down to at least 10 m.

How it lives

It lives alone and hunts mostly at night, eating mainly crabs. It is often seen with only its head poking out of a hole.

Easy to confuse with

• Zebra Moray (Gymnomuraena zebra): Dark brown with thin white rings.
• Other morays (Gymnothorax): Usually brown, spotted or plain, with long sharp teeth, never the black-and-yellow snowflake pattern.

How to recognise it

• A bluish-grey body ringed all the way round with even black bands.
• Yellow snout and upper lip, with a yellow bar running back from the eye.
• A flat, paddle-shaped tail.

Where to find it

On coral reefs and rocky shores. It rests in rock cracks near the water's edge and under rocks and plants on land.

How it lives

It spends much of its time on land and goes back to sea to hunt. Females mostly catch single big conger eels; males eat several smaller moray eels.

Easy to confuse with

• Blue-lipped Sea Krait (Laticauda laticaudata): Same bands, but a dark upper lip, and it comes ashore less often.
• True sea snakes (Hydrophis): Rarely leave the water, and have small belly scales.

The law

Sea kraits are protected under Schedule II of the Wild Life (Protection) Act, which covers all elapid snakes except the cobras and King Cobra (those are in Schedule I).

How to recognise it

• A carpet of small flower-like polyps joined at the base.
• A smooth body with no sand in it (unlike Palythoa).
• Short tentacles in about two rows around a smooth disc, often a different colour from the disc.
• At low tide the polyps close up and look like small blobs.

Where to find it

On stones, coral rubble and under seagrass on the lower shore and reef flats, sometimes as carpets several square metres across.

How it lives

Most of its food comes from tiny algae living inside its tissue, which make food from sunlight. The polyps close and pull in when the tide goes out and open again when it comes back.

Easy to confuse with

• Sandy zoanthids (Palythoa): They build sand into their bodies, so they feel gritty and sit in a thick mat. Some are highly toxic.
• Small sea anemones: Anemones live alone. Zoanthids are many polyps joined together.

The law

All stony corals, blue coral, fire coral and zoanthids, and the soft-coral and sea-fan families named in the Act, are in Schedule I of the Wild Life (Protection) Act, the highest level of protection in India. Breaking, collecting or carrying coral, even a dead piece from the beach, is an offence. Stand on sand or bare rock, never on coral.

How to recognise it

• A small bushy colony on a short stalk.
• Branches end in egg-shaped lobes covered in tiny polyps.
• A pale stalk with lines running along it.
• Light brownish grey.

Where to find it

On reef flats with dead coral rock and sand-rubble, from the tide zone into shallow water.

How it lives

It catches tiny food from the water flowing past, and like many shallow corals it also gets food from algae living in its tissue.

Easy to confuse with

• Other bushy soft corals (Litophyton, Nephthea): Very similar. Only the sclerites under a microscope tell them apart.
• Finger Leather Coral: A stiff, leathery mat with finger-like lobes, not lobes on thin pale stalks.

The law

All stony corals, blue coral, fire coral and zoanthids, and the soft-coral and sea-fan families named in the Act, are in Schedule I of the Wild Life (Protection) Act, the highest level of protection in India. Breaking, collecting or carrying coral, even a dead piece from the beach, is an offence. Stand on sand or bare rock, never on coral. The Act lists Capnella under its older family name, Nephtheidae.

How to recognise it

• Looks like a hard coral: lumps, thick upright plates or columns.
• Outside usually brown or grey-brown, not blue.
• Tiny holes, about 2 mm, all over the surface, where the polyps sit.
• The skeleton inside is blue (you would only see it if it broke; never break it).

Where to find it

Among hard corals on reef flats and shallow reefs. In places it is exposed at low tide.

How it lives

Its polyps have eight feathery tentacles, like soft corals. Most of its food comes from algae living in its tissue. It usually suffers less than hard corals in mass bleaching.

Easy to confuse with

• Fire Coral: Usually mustard-yellow with pale tips, and it stings. Blue coral is grey-brown and does not sting.
• Boulder Pore Coral (Porites): Tiny cups packed edge to edge, not scattered round pores.

The law

All stony corals, blue coral, fire coral and zoanthids, and the soft-coral and sea-fan families named in the Act, are in Schedule I of the Wild Life (Protection) Act, the highest level of protection in India. Breaking, collecting or carrying coral, even a dead piece from the beach, is an offence. Stand on sand or bare rock, never on coral.

How to recognise it

• A flat fan of red or orange branches growing in one plane.
• Tiny white polyps dotted along the branches.
• Swollen joints, or "knots", along the branches.

Where to find it

On rock just past the low-tide line and deeper. We found no Andaman source giving its exact depth here.

How it lives

The fan grows across the current, and its polyps catch very small particles of food from the water passing through.

Easy to confuse with

• Other sea fans (Annella, Subergorgia): Usually brown or yellow and much bigger.

The law

All stony corals, blue coral, fire coral and zoanthids, and the soft-coral and sea-fan families named in the Act, are in Schedule I of the Wild Life (Protection) Act, the highest level of protection in India. Breaking, collecting or carrying coral, even a dead piece from the beach, is an offence. Stand on sand or bare rock, never on coral.

How to recognise it

• Stiff, solid, turban- or top-shaped blades crowded round an upright stem.
• The edges of the blades are often spiny.
• Golden to olive brown.

Where to find it

On rocks and boulders near the low-tide mark, including spots hit by strong waves, and in sheltered lagoons.

How it lives

Like other seaweeds it makes its own food from sunlight. It is not a plant in the strict sense but a brown alga.

Easy to confuse with

• Turbinaria conoides: Very similar. You need a close look at the blades.
• Sargassum: Thin flat leaves and small round air bladders, not stiff turban-shaped blades.

How to recognise it

• Strap-like leaves that curve slightly, like a sickle.
• Rounded, smooth leaf tips.
• Leaves often speckled with tiny dark dots.
• Thick pinkish-white stems under the sand.

Where to find it

In shallow meadows from the tide zone down to about 2.5 m, often on coarse sand mixed with rubble.

How it lives

Snails graze the algae that coat its leaves, and dugongs and green turtles eat the seagrass itself. Meadows like this are nurseries for many young fish.

Easy to confuse with

• Cymodocea seagrass: Straighter, thinner leaves without the curve.
• Tape Seagrass: Much longer, wider leaves and black bristly stems.

How to recognise it

• A big rounded boulder or helmet shape with a smooth surface.
• Cream or yellow, sometimes brighter colours in shallow water.
• Covered in tiny pin-hole cups, 1-2 mm across.
• On reef flats: a flat-topped ring with a dead centre and a living edge.

Where to find it

On reef flats, back-reef edges and lagoons. On reef flats it grows up until it meets the low-tide level, then the top dies back and it keeps growing sideways.

How it lives

Most of its food comes from algae in its tissue, and its tiny polyps put out tentacles mostly at night. It sheds a layer of slime to clean off sand.

Easy to confuse with

• Porites lobata: Very similar boulders. Experts look at the tiny cups.
• Blue Coral: Plates and columns with scattered round pores, not packed pin-holes.

The law

All stony corals, blue coral, fire coral and zoanthids, and the soft-coral and sea-fan families named in the Act, are in Schedule I of the Wild Life (Protection) Act, the highest level of protection in India. Breaking, collecting or carrying coral, even a dead piece from the beach, is an offence. Stand on sand or bare rock, never on coral.

How to recognise it

• A smooth crust, plates or branches, mustard-yellow to brown.
• Pale or whitish tips and edges.
• Underwater, fine "hairs" (stinging polyps) cover the surface.
• It can coat rocks and dead coral, so it may not look like a branching coral at all.

Where to find it

On hard surfaces on shallow reefs, including rock and dead coral.

How it lives

Its polyps catch tiny animals with stinging cells, and it also gets food from algae in its tissue.

Easy to confuse with

• Blue Coral: Grey-brown, without the stinging fuzz, and harmless to touch (but protected).
• Plate corals (Montipora): They show coral cups. Fire coral is smooth with pin-prick pores.

The law

All stony corals, blue coral, fire coral and zoanthids, and the soft-coral and sea-fan families named in the Act, are in Schedule I of the Wild Life (Protection) Act, the highest level of protection in India. Breaking, collecting or carrying coral, even a dead piece from the beach, is an offence. Stand on sand or bare rock, never on coral.

How to recognise it

• A big wavy "carpet" covered in short tentacles, about 1 cm long.
• Slender, pointed tentacles that stick to your skin.
• Brown or purplish tentacles with paler tips.
• Rows of brightly coloured bumps on the side of the body.

Where to find it

On coral rubble, gravel and sand near reefs, from the low-tide zone down to about 20 m. The body is buried in a crack, so the disc can pull back when disturbed.

How it lives

Most of its food comes from algae in its tissue. It gives a home to clownfish and peacock-tail anemone shrimps, which are protected by its stinging tentacles.

Easy to confuse with

• Haddon's Carpet Anemone (Stichodactyla haddoni): On sand and seagrass, with short stubby tentacles and a fringe of longer ones at the edge.
• Merten's Carpet Anemone (Stichodactyla mertensii): Up to 1 m across, usually deeper, and its tentacles are not sticky.

How to recognise it

• Bunches of small green beads like tiny grapes.
• The bunches rise from a long creeping runner.
• Beads round or club-shaped, loosely packed.
• Green to yellow-green or blue-green.

Where to find it

On rocks and coral rubble in small clumps, sometimes creeping onto sand.

How it lives

A green seaweed that makes its own food from sunlight. The whole runner can be a single cell, very long, with many nuclei.

Easy to confuse with

• Round Sea Grapes (Caulerpa lentillifera): Beads packed tightly and neatly, each with a clear "neck".
• Coin Seaweed (Halimeda): Hard, flat, coin-like segments, not soft beads.

How to recognise it

• Chains of flat, coin-like green segments.
• The segments are hard and chalky; the joints between them bend.
• Shapes vary from round coins to crinkly fans.
• Dead segments turn white.

Where to find it

On coral rubble, among living corals and on sand near reefs, sometimes in clumps 40-50 cm wide.

How it lives

It can grow a new segment in a day or two. Chemicals in it put off most grazers, though some sea slugs eat it.

Easy to confuse with

• Sea Grapes: Soft green beads on a runner, not hard flat coins.

How to recognise it

• A bunch of small funnel- or fan-shaped blades.
• Fine lines of tiny hairs in rings across the fan.
• A rolled edge, often torn.
• Golden brown with a whitish, chalky tinge.

Where to find it

On boulders, rocks, stones and coral rubble on the lower shore.

How it lives

A brown seaweed that makes its own food from sunlight.

Easy to confuse with

• Lobophora: Flat, leathery brown crusts without the rings of hairs or the chalky tinge.

How to recognise it

• Long, flat ribbon leaves, slightly rolled at the edges.
• Thick stems covered in stiff black bristles (old leaf fibres).
• Thick, cord-like roots.

Where to find it

From the tide zone down to about 5 m, on fine sand, especially in sheltered bays.

How it lives

It is thought to be one of the main foods of the dugong. Algae and tiny animals grow on its leaves.

Easy to confuse with

• Sickle Seagrass: Much shorter, curved leaves and no black bristles.

How to recognise it

• A firm, leathery, rubbery colony with no hard skeleton.
• Many finger- or knob-like lobes (the shape varies).
• Smooth when the polyps are pulled in at low tide.
• Usually grey, brown or greenish.

Where to find it

On shallow reef flats and rocky reef areas in the tide zone and just below.

How it lives

Most of its food comes from algae living in its tissue. Its polyps pull in when it is out of water.

Easy to confuse with

• Mushroom Leather Coral (Sarcophyton): A smooth mushroom-like cap on a stalk, not many fingers.
• Lobophytum leather coral: A thick crust with ridges and no stalk.

The law

All stony corals, blue coral, fire coral and zoanthids, and the soft-coral and sea-fan families named in the Act, are in Schedule I of the Wild Life (Protection) Act, the highest level of protection in India. Breaking, collecting or carrying coral, even a dead piece from the beach, is an offence. Stand on sand or bare rock, never on coral. The Act lists Sinularia under its older family name, Alcyoniidae.