Snorkelling in Thailand: What You Will Actually See

Green Sea Turtle Regular Endangered

Chelonia mydas

The great grazing turtle of the tropics, the only sea turtle that turns vegetarian as an adult.

Where: Shallow reef and seagrass around Phi Phi Don. Best: Nov-Apr, nesting Nov-Feb.

Hawksbill Turtle Occasional Critically Endangered

Eretmochelys imbricata

The reef's sponge specialist, its beautiful shell also the reason it was hunted to the edge.

Where: Coral bommies at Bida Nok. Best: Nov-Apr.

Giant Clam Occasional Critically Endangered

Tridacna gigas

The largest shellfish on Earth, a metre-wide clam that farms algae in its own rippling, jewel-coloured flesh.

Where: Shallow reef tops. Best: Nov-Apr.

Blacktip Reef Shark Common Vulnerable

Carcharhinus melanopterus

The neat little reef shark of the shallows, its black-tipped fins often cutting the surface over sun-lit sand flats.

Where: Shallow reef flats at Maya Bay and around Koh Phi Phi Ley. Best: Nov-Apr, early morning, best Dec-Mar. Maya Bay's shark nursery is the most reliable shark snorkel in Thailand. Go at opening time.

Whitespotted Bamboo Shark Occasional Endangered

Chiloscyllium plagiosum

A small, slow shark that walks along the bottom on its fins and can survive hours in a tide pool with almost no oxygen.

Where: Under ledges at night. Best: Nov-Apr, night dives.

Bluestreak Cleaner Wrasse Common

Labroides dimidiatus

A tiny striped wrasse that runs the reef's health clinic, picking parasites from fish that queue up and even open their mouths for it.

Where: Cleaning stations throughout. Best: Nov-Apr.

False Clownfish (Clown Anemonefish) Common

Amphiprion ocellaris

The famous orange and white anemonefish, immune to the stinging tentacles that shelter it and every group ruled by a single dominant female.

Where: Anemones on the shallow reef. Best: Nov-Apr.

Moorish Idol Common

Zanclus cornutus

An unmistakable disc of black, white and gold trailing a long ribbon fin, one of the most elegant fish on any reef.

Where: Reef throughout. Best: Nov-Apr.

Chromodoris Nudibranch Regular

Chromodoris species

A tiny sea slug in outrageous colours that borrows toxins from the sponges it eats and flaunts them as a warning.

Where: Sponges on the walls. Best: Nov-Apr.

Green Sea Turtle Regular Endangered

Chelonia mydas

The great grazing turtle of the tropics, the only sea turtle that turns vegetarian as an adult.

Where: Seagrass and shallow reef at Donald Duck Bay and Anita's Reef. Best: Nov-Apr, nesting Nov-Feb.

Zebra Shark (Leopard Shark) Regular Endangered

Stegostoma tigrinum

A gentle, spotted shark that lies on the sand like a giant lazy cat, striped as a pup and spotted as an adult.

Where: Sandy patches at East of Eden, Anita's Reef and Elephant Head Rock. Best: Nov-Apr, morning dives, best Dec-Mar. Rests on sand in the open; approach slowly from the side and it will usually stay.

Hawksbill Turtle Occasional Critically Endangered

Eretmochelys imbricata

The reef's sponge specialist, its beautiful shell also the reason it was hunted to the edge.

Where: Coral bommies and sponge-covered walls throughout. Best: Nov-Apr.

Ocellated Eagle Ray Occasional Endangered

Aetobatus ocellatus

A dramatic ray that flies through open water on wings spangled with white spots, trailing a whip-like venomous tail.

Where: Drop-offs at Koh Bon and Christmas Point. Best: Nov-Apr, more frequent Feb-Apr. Usually passing in open water; look out into the blue on every safety stop.

Bumphead Parrotfish Occasional Vulnerable

Bolbometopon muricatum

A hulking, bull-headed parrotfish that rams and bites living coral, turning reef rock into the white sand of tropical beaches.

Where: Reef tops at dawn on the outer islands. Best: Nov-Apr, first dive of the day. Best on the first dive of the day, before the schools break up.

Humphead Wrasse (Napoleon Wrasse) Rare Endangered

Cheilinus undulatus

A giant, curious reef fish with thick lips and a bulging forehead, able to crunch prey that few other animals can eat.

Where: Outer reef slopes at Koh Bon and Christmas Point. Best: Nov-Apr, best in calm Feb-Apr water. Large individuals are curious and will follow a diver.

Reef Manta Ray Occasional Vulnerable

Mobula alfredi

A four metre wingspan gliding overhead in slow, hypnotic loops that leave divers grinning for days.

Where: Koh Bon and Koh Tachai. Best: Feb-Apr, occasional from Jan.

Ribbon Eel Occasional

Rhinomuraena quaesita

A ribbon of electric blue and yellow that sways from a hole in the sand, and remarkably changes sex and colour as it grows.

Where: Sand and rubble margins at Anita's Reef. Best: Nov-Apr. Blue adults and black juveniles occupy the same burrows for months.

Green Sea Turtle Regular Endangered

Chelonia mydas

The great grazing turtle of the tropics, the only sea turtle that turns vegetarian as an adult.

Where: Seagrass and shallow reef around Koh Tao and the Ang Thong islands. Best: Feb-Sep, best Apr-Aug.

Blacktip Reef Shark Common Vulnerable

Carcharhinus melanopterus

The neat little reef shark of the shallows, its black-tipped fins often cutting the surface over sun-lit sand flats.

Where: Shark Bay on Koh Tao and shallow reef flats. Best: Year round, best Feb-Sep. Shark Bay is a snorkel, not a dive, and the sharks are there most mornings.

Jenkins Whipray Occasional Vulnerable

Pateobatis jenkinsii

A big sand-flat ray with a ridge of enlarged thorns down its spine and a tail twice the length of its body.

Where: Sand flats between coral heads. Best: Year round, best Feb-Sep.

Indo-Pacific Horseshoe Crab Rare Endangered

Tachypleus gigas

Not a crab at all, closer to a spider, and its blue blood is used worldwide to test every injectable drug for contamination.

Where: Muddy shores on spring tides. Best: Around the full and new moon.

Blue Coral Occasional Vulnerable

Heliopora coerulea

The only coral on earth with a blue skeleton, hidden under brown tissue until the animal dies.

Where: Shallow high-energy reef. Best: Year round, best Feb-Sep.

Table Coral Common Near Threatened

Acropora hyacinthus

Grows outward faster than it grows up, spreading a flat platform that shades out every competitor beneath it.

Where: Shallow reef around Koh Tao. Best: Year round, best Feb-Sep.

Pyjama Cardinalfish Regular

Sphaeramia nematoptera

Looks like three different fish stitched together, and the male holds the whole clutch of eggs in his mouth for a week.

Where: Branching coral in the shallows. Best: Year round, best Feb-Sep.

Cowtail Stingray Occasional Vulnerable

Pastinachus sephen

Named for the broad flap of skin hanging under its tail like a cow's tail, unique among rays.

Where: Sandy shallows and seagrass. Best: Year round, best Feb-Sep.

Flamboyant Cuttlefish Rare

Metasepia pfefferi

The only cuttlefish known to be poisonous to eat, and it advertises the fact in pulsing purple, yellow and red.

Where: Silty sand on muck dives. Best: Feb-Sep, muck sites.

Green Sea Turtle Regular Endangered

Chelonia mydas

The great grazing turtle of the tropics, the only sea turtle that turns vegetarian as an adult.

Where: Seagrass meadows around Koh Libong and Koh Muk. Best: Nov-Apr, best Dec-Mar on the seagrass.

Dugong Occasional Vulnerable

Dugong dugon

The gentle sea cow said to have inspired mermaid legends, grazing seagrass meadows in warm shallow seas.

Where: Seagrass meadows off Koh Libong, from a longtail at high tide. Best: Dec-Apr, calm mornings on a spring tide. Thailand's most important dugong population. Local boatmen at Koh Libong know the feeding trails.

Blacktip Reef Shark Common Vulnerable

Carcharhinus melanopterus

The neat little reef shark of the shallows, its black-tipped fins often cutting the surface over sun-lit sand flats.

Where: Shallow reef flats around the islands. Best: Nov-Apr. Often visible from the surface on a snorkel in knee-deep water.

Porcupine Ray Rare Vulnerable

Urogymnus asperrimus

The only large stingray with no sting at all, protected instead by a hide of blunt thorns.

Where: Sand flats near seagrass. Best: Nov-Apr.

Sicklefin Lemon Shark Rare Endangered

Negaprion acutidens

A heavy, yellow-brown shark that uses mangrove shallows as a nursery and barely moves out of them for the first years of life.

Where: Sandy shallows and mangrove edges. Best: Nov-Apr.

Magnificent Sea Anemone Common

Heteractis magnifica

A great carpet of stinging tentacles that is home and fortress to the anemonefish, a partnership at the heart of the reef.

Where: Shallow reef. Best: Nov-Apr.

Staghorn Coral Common

Acropora species

The fast-growing branching coral that builds the living thickets of the reef, nursery and shelter for a whole community.

Where: Shallow reef flats. Best: Nov-Apr.