Thailand

Diving in Koh Tao

26 sites89 species27–30 °C5–25 m vis

Photo: mirthe diender / Pexels

Koh Tao (Turtle Island) is the Gulf of Thailand's diving mecca and the world's most prolific diver certification destination — certifying more new divers per square kilometer than anywhere on Earth. This granite boulder island in the Chumphon Archipelago offers 26+ named dive sites from shallow beginner bays to offshore pinnacles attracting whale sharks. The dramatic underwater terrain features massive granite formations, swim-throughs, caverns, and the iconic Sail Rock chimney. Water temperatures hold steady at 27–30°C year-round with visibility from 5m to 25m. The island's compact size (21 km²) and dense concentration of dive centers (21+ PADI/SSI operators) make it the most accessible and affordable dive training hub in Southeast Asia. Home to its own hyperbaric chamber and healthy populations of reef sharks, turtles, and seasonal whale sharks (peak March), Koh Tao combines world-class diving with Thailand's signature hospitality at backpacker-friendly prices.

Koh Tao means 'Turtle Island' in Thai — named both for its turtle-like shape when viewed from Koh Pha-ngan and for being an important nesting ground for hawksbill and green sea turtles.Koh Tao certifies more new divers per year than anywhere else on Earth — an estimated 30,000+ Open Water certifications are issued annually, earning it the nickname 'Diver Factory.'The HTMS Sattakut wreck was a WWII-era US Navy Landing Craft Infantry that served in the Pacific theater before being transferred to Thailand and scuttled as an artificial reef in 2011.The island's underwater granite boulder formations are part of the same geological complex as the famous granite karsts of Phang Nga Bay, formed over 200 million years ago during the Triassic period.The Green Rock 'cathedral' is a large open chamber in the boulder maze where divers can surface into an air pocket — one of only a handful of such underwater air chambers accessible to recreational divers in Thai waters.Koh Tao's turtle population is supported by an active Royal Thai Navy hatchery and release program operating since 2004, which has released thousands of juvenile turtles back into the wild.Sail Rock's famous 'chimney' is a vertical shaft through solid granite — divers can enter at 5m, 13m, or 19m and exit around 12m, making it one of the most unusual swim-throughs in Southeast Asia.The island has no airport — all visitors arrive by ferry from Chumphon (1.5–3 hours), Koh Samui (2.5 hours), or Koh Pha-ngan (1.5–2 hours), contributing to Koh Tao's off-the-beaten-path charm.

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Places on this map (44)

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Conditions

Water temp

27–30 °C

Visibility

5–25 m

Depth

2–40 m

Current

Moderate

Best season

December to March for best visibility and calm seas; February to April for whale sharks

Month	Summary
Jan	Peak dry season conditions: 27°C water, 15–25m visibility, calm seas. Whale shark season begins. All sites accessible including offshore pinnacles. A 3mm wetsuit is sufficient for most divers. Busy period — book dive packages in advance.
Feb	Excellent conditions continue: 27°C water, 15–25m visibility. Prime whale shark month. Best month for offshore pinnacles (Chumphon, Sail Rock) with calmest seas. Water begins warming slightly by late February.
Mar	Peak whale shark month — Koh Tao's best month overall for diving. 28°C water, 15–25m visibility, calm seas. All marine life at maximum activity. Whale shark encounters most frequent. Book well ahead — this is the busiest diving month.
Apr	Hot season begins: 29°C water, 12–20m visibility. Whale shark sightings continue, conditions still very good. Water warm enough for rash guard or 3mm shorty. Songkran (Thai New Year) mid-month brings festive atmosphere. Slightly lower crowds than March.
May	Warm water at 29°C, visibility 12–20m. Good diving conditions continue. Triggerfish nesting season — maintain distance from nests (aggressive territorial behavior). Water warmest for shallow reef dives. Monsoon still distant.
Jun	Early monsoon transition: 29°C water, 10–18m visibility. Conditions remain diveable on west coast and protected bays. East coast sites may experience wind chop. Offshore pinnacles still accessible most days. Fewer tourists — more relaxed pace.
Jul	Monsoon conditions: 29°C water, 10–18m visibility. Windier with rougher seas, especially on east coast. West coast and protected bays (Japanese Gardens, Mango Bay, Twins) remain reliably diveable. Offshore pinnacles may be canceled on windy days. Low tourist season — uncrowded sites and discounted packages.
Aug	Peak monsoon: 29°C water, 10–18m visibility. Roughest sea conditions of the year. Stick to sheltered west coast and Nangyuan sites. Offshore trips limited — check daily with dive operators. Warmest water temperatures make for comfortable shallow diving. Lowest prices of the year.
Sep	Monsoon easing: 28°C water, 8–15m visibility. Transitional month — conditions improving through September. West coast sites still the best option. Offshore pinnacles begin reopening by late September. Lower visibility but rich plankton brings more pelagics. Good month for macro photography.
Oct	Monsoon transition ending: 28°C water, 8–15m visibility. Variable conditions — can be excellent or rough depending on weather patterns. Offshore sites reopening. Leopard shark season begins around HTMS Sattakut. Shoulder season pricing — good value.
Nov	Dry season approaching: 27°C water, 10–18m visibility. Conditions improving rapidly — seas calming, visibility clearing. Leopard sharks regular at Lighthouse Bay, Red Rock, and Sattakut wreck. Excellent value month with good conditions and low crowds. 5mm wetsuit recommended as water cools.
Dec	Dry season returns: 27°C water, 12–20m visibility. Excellent diving conditions returning across all sites including offshore pinnacles. Christmas and New Year period is very busy — book well ahead. Cooler air temperatures make surface intervals pleasant. A 3mm wetsuit comfortable for most.

Dive Sites (26)

Ao Leuk (Au-Luuk Bay)

2–20m · Beginner

Sandy bay · Coral garden · Shore dive

Ao Muong

3–14m · Beginner

Sandy bay · Patch reef · Shore dive

Ao Tien (Sunrise Beach)

2–12m · Beginner

Sandy bay · Patch reef · Shore dive

Chalok Baan Khao Bay

3–14m · Beginner

Sandy bay · Patch reef · Shore dive

Chumphon Pinnacle

14–36m · Advanced

Pinnacle · Pelagics · Boulders

Freedom Beach

3–15m · Beginner

Sandy bay · Seagrass · Coral garden

Green Rock

5–26m · Beginner

Boulders · Swim-throughs · Cavern

Hin Daeng

5–28m · Intermediate

Coral garden · Swim-throughs · Arch

+18more sites in the appGet the app →

Marine Life (89)

must-see

Atlantic Bottlenose Dolphin

must-see

Loggerhead Turtle

must-see

Great Hammerhead

must-see

Bull Shark

must-see

Hawksbill Turtle

must-see

Green Sea Turtle

must-see

Spotted Eagle Ray

must-see

Crowned Jellyfish

Common Lionfish

Great Barracuda

Blue-ring Angelfish

Spotted Coral Grouper

+77more species in the app

Dive Shops (34)

Big Blue Diving School Koh Tao

★ 5Moderate

Diving in Koh Tao

Explore the map

Conditions

Dive Sites (26)

Ao Leuk (Au-Luuk Bay)

Ao Muong

Ao Tien (Sunrise Beach)

Chalok Baan Khao Bay

Chumphon Pinnacle

Freedom Beach

Green Rock

Hin Daeng

Marine Life (89)

Dive Shops (34)

Big Blue Diving School Koh Tao

Ban's Diving Resort

Taco Divers Koh Tao

Sairee Cottage Diving

Simple Life Divers

DPM Diving Koh Tao

Nitro Dive Center - Koh Tao

Mojo Diver - Koh Tao Diving Centre(Main Centre)

Turtle Divers - Koh Tao

Carabao Dive Resort

Taco Shack Diving Hostel & Restaurant

Dive Onda

Pura Vida Diving

Go Diving Koh Tao - Scuba & Freediving Centre

La Bombona Diving - Scuba Diving Center - Koh Tao - Thailand

Goodtime Adventures | Scuba Diving, Snorkeling, & Climbing

Phoenix Divers

NAVA Scuba Diving

Echo Divers Koh Tao

Deutsche Abteilung - www.bansdiving.de

ONYX Divers Koh Tao

Hydronauts Diving Resort

Hang Loose Divers - Koh Tao Scuba Diving Center

The Diver's Boat

French Kiss Divers - Koh Tao

Kaizen Freediving Koh Tao Thailand

Deep Dive Center at Koh Tao Montra

Calypso Diving Koh Tao

Crystal Dive Koh Tao

Islander Hostel & Dive School

Coral Grand Divers - Koh Tao PADI Career Development Center

Diving Koh Tao

IDC Koh Tao | Divemaster & Instructor

Scubadoo Koh Tao

Guides

Top 12 Dive Sites in Koh Tao: Ranked for Every Level

Koh Tao Diving Conditions: Temperature & Seasons Guide

The Complete Guide to Diving Koh Tao: Sites, Species & Costs

Safety

Bring Koh Tao underwater