Twenty years of being on and in the Andaman Sea means I have had time to learn what is out there. The marine environment around Phuket and the Phi Phi Islands is genuinely extraordinary — not just impressive by tourist-experience standards but actually diverse and abundant in ways that surprise people who have snorkelled elsewhere in the world.
Here is the guide to what you are likely to encounter, from the reliable everyday species to the occasional encounters worth slowing down for.
The most visually striking common reef fish of the Andaman. Parrotfish grow large — often 40 to 60 centimetres — and come in colours that look digitally enhanced: turquoise, pink, green, orange, sometimes several at once. They feed on coral algae by biting directly into the coral, which produces the fine white sand on many of the region’s beaches. You can hear them feeding from the surface. Look for the fused beak-like mouth that gives them their name.
The electric blue tang and its relatives are among the most common and most beautiful fish on the reef. They travel in schools, often mixed with other species, and the movement of a large school through clear water — the light catching hundreds of iridescent blue bodies — is one of those sights that makes people stop swimming and just float and watch.
Nemo. Everyone’s first question. Yes, they are here, and yes, they really do live in anemones and really do dart back inside if you get too close. The symbiotic relationship between clownfish and sea anemone is one of the most photographed things in the ocean around Phuket. Give the anemone a metre of space, float quietly, and the clownfish will come out to investigate you rather than the other way around.
Usually visible as a head emerging from a gap in the coral — wide mouth opening and closing rhythmically, which is how they breathe rather than a threatening gesture. Spotted morays and geometric morays are the most common species around Phi Phi. They are curious rather than aggressive and will retreat if approached directly. Look for them in crevices at the base of coral formations.
Solidly built, strongly patterned, and possessing a bite that is genuinely powerful. The titan triggerfish, which nests in sandy patches among the coral, is the one to respect — they defend their nesting territory actively. If a large triggerfish starts swimming toward you in an agitated way, swim horizontally away from the nest area rather than upward, as the territory extends in a cone above the nest. The clown triggerfish, by contrast, is beautiful and rarely aggressive.
The green sea turtle is the species you are most likely to encounter around Phi Phi and the Racha Islands. They surface to breathe every few minutes and often rest on the coral or on the sandy bottom. The protocol everyone who cares about marine life agrees on: do not chase, do not reach out to touch, stay still and let them approach. A turtle that has not been harassed will often swim directly toward a stationary snorkeller out of curiosity, which is a significantly more extraordinary experience than a turtle swimming away from someone who is pursuing it.
Small — typically 1 to 1.5 metres — and entirely harmless to snorkellers. They often cruise along the sandy channels between coral formations, following the current. First-time sighters usually freeze, then laugh at themselves, then try to follow it, which achieves nothing because the shark is considerably faster than any snorkeller. The correct response is to float still and watch. They are beautiful and they are not interested in you.
The masters of camouflage. Look carefully at rocky substrate and coral rubble at the edges of the reef — an octopus in hunting mode moves in short darts, changing colour and texture as it goes. Finding one requires slowing down and looking at the reef differently, which is good practice for all reef snorkelling. Once you have spotted your first octopus in the wild, you will look for them on every dive.
Occasionally seen cruising over the sandy open areas between reef systems, eagle rays are among the most graceful large animals in the Andaman. Spotted eagle rays — dark on top with white spots, long tail, wingspan of a metre or more — are occasionally seen at Phi Phi and the Racha Islands. They move with an ease that makes flying seem like the right description. If you see one, stop moving and watch it pass.
Whale sharks are seen occasionally in the deeper water beyond the Phi Phi archipelago and more reliably around the Similan Islands and Richelieu Rock. Manta rays are seen seasonally, primarily around the outer reefs. Dugong — large, gentle marine mammals that graze on seagrass — are occasionally sighted in the shallow areas of Phang Nga Bay. These are not trips I would book specifically to see, but encounters that may happen if you spend enough time in the right water.
Do not touch anything. Not the coral, not the fish, not the anemones. The oils on human skin are harmful to coral, and handling marine animals causes stress responses that are not visible to the observer but are real for the animal.
Move slowly. Everything worth seeing in the water sees you first. Fast movement scatters fish and disturbs the reef environment. The snorkellers who see the most are almost always the ones moving the least.
➤ Phi Phi Day Trip — The best marine life accessible from Phuket
For the best snorkelling spots across the region, our guide to the top 10 snorkelling destinations in Phuket covers where to find what.
— Captain Mark
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