The marine life of Koh Tao is one of the main reasons divers from around the world come back to this island year after year. Whale sharks, green turtles, barracuda tornadoes, giant groupers — all within a two-hour boat ride from Mae Haad. Here are the species you’re most likely to encounter, and where to find them.
Dive sites
Water year-round
Whale sharks
Green turtles
🦈 Whale shark — the star of Koh Tao marine life
It’s the animal everyone hopes to see. The whale shark (Rhincodon typus) is the world’s largest fish — up to 18 metres — and feeds exclusively on plankton. Completely harmless. When one arrives, you stop kicking and watch it pass. That’s all there is to do, and it’s more than enough.
When: Year-round — peaks March–May and October–November
Our record: Two simultaneously at Sail Rock in April
🐢 Green turtle — the most relaxed Koh Tao marine life encounter
The green turtle (Chelonia mydas) is probably the most photographed animal in Koh Tao — and rightly so. It grazes on seagrass in slow motion, completely indifferent to divers, and regularly surfaces to breathe. An encounter with a turtle at 6 metres depth is accessible from your very first dive.
When: Year-round — permanent presence on several sites
Level required: All levels, from try scuba
🐟 Barracudas — the spectacle of Koh Tao marine life
Chevron barracudas (Sphyraena barracuda) move in dense schools around the pinnacles, sometimes forming slow silver tornadoes spinning in the blue. Up close they’re striking — large, fast, with that prominent jaw. They ignore divers completely. They’re the ones watching us, not the other way around.
When: Year-round on pelagic sites
Level required: Open Water minimum
🐟 Giant groupers — the elders of Koh Tao marine life
Some groupers at Chumphon Pinnacle and Sail Rock are surprisingly large — 80 centimetres, sometimes more. They’ve held their territory for years and don’t move for much. You can get within a few dozen centimetres and they just look back at you with that expression of a fish that has seen everything. Malabar grouper (Epinephelus malabaricus) and marbled grouper (Epinephelus polyphekadion) are the two most common species.
When: Year-round — they don’t migrate
Level required: All levels
🐟 Batfish — the curious ones of Koh Tao marine life
Batfish (Platax teira) are impossible to miss — almost circular, very flat, and with a disconcerting curiosity about divers. They come close, circle around you, stare. They’re said to be attracted by the reflections of dive instruments. You’ll often find them in groups inside the Sail Rock chimney, hovering mid-water as you ascend.
When: Year-round
Level required: All levels
🐍 Moray eels — the hidden Koh Tao marine life
The giant moray (Gymnothorax javanicus) is everywhere in Koh Tao — in every crack, under every overhang. It opens and closes its mouth continuously, not to threaten, but to circulate water over its gills. An experienced guide knows exactly where to look. Many divers swim straight past without spotting them.
When: Year-round
Level required: All levels
🟠 Clownfish — the guardians of Koh Tao marine life
The clownfish (Amphiprioninae) lives in symbiosis with anemones and never leaves them. It defends them with an aggression inversely proportional to its size — an 8-centimetre fish charging at your mask is genuinely surprising the first time. Host anemones are present on most shallow sites in Koh Tao, particularly Japanese Garden and Twins.
When: Year-round
Level required: All levels, from try scuba
🌊 Rays — the surprise of Koh Tao marine life
The blue-spotted ribbontail ray (Taeniura lymma) is the most commonly seen — resting on the sand, half-hidden, perfectly still until a curious diver gets too close. Stingrays (Dasyatis) are also frequent on sandy bottoms. On the pelagic side, eagle rays (Aetobatus narinari) pass regularly at Chumphon Pinnacle.
When: Year-round
Level required: All levels
⚡ Giant trevally — the hunters of Koh Tao marine life
Giant trevally (Caranx ignobilis) hunt in formation — fast, silver, coordinated. They sweep through schools of smaller fish with a precision that impresses every time. They’re found mainly on exposed pelagic sites, often alongside barracudas. At Samran Pinnacle, schools can number several dozen individuals.
When: Year-round on pelagic sites
Level required: Open Water minimum
Marine life doesn’t take requests. But some things help: a guide who genuinely knows the site, small groups (4 divers max with us), and the patience to stay still for a few seconds rather than kicking around everywhere. Animals approach calm divers. That’s true for turtles, groupers, and occasionally — whale sharks too.
We go out every day from Koh Tao and Koh Phangan. Tell us your level and your dates — we’ll suggest the sites where you’re most likely to encounter the species you’re after.
📞 +66 828 149 282 · 🌐 thediversboat.com
