Koh Samui offers easy access to several reef areas, and the nearby islands Ko Madsum and Ko Tean are reachable within 15-30 minutes by boat. The Gulf of Thailand is warm and relatively clear during the dry season, making snorkelling possible almost year-round.

Best Snorkelling Spots

Ko Madsum

A small uninhabited island south of Samui and one of the region's top snorkelling destinations. Visibility up to 15-20 m on a calm day, coral reefs with butterflyfish, clownfish, sea urchins and starfish. The island is also known for its resident pigs fed by tourists. Travel time: about 20 minutes by speedboat.

Ko Tean

Adjacent to Ko Madsum and slightly larger. Snorkelling is particularly good on the island's eastern side, where the reef begins just metres from shore at 1-3 m depth. Look for cuttlefish, stingrays and large parrotfish. Tours frequently combine both islands in one trip.

Ang Thong Marine National Park

A national park 30 km north-west of Samui comprising 42 islands. Snorkelling here is exceptionally rich: coral gardens, emerald lagoons, sea turtles. Day tours depart from Na Thon pier daily October-May, costing 1,200-1,800 THB including boat, lunch and mask.

Choeng Mon Bay

A small reef sits at the right side of Choeng Mon bay, accessible directly from the beach beyond the buoy line. Visibility depends on the tide and time of day.

Tours and Independent Snorkelling

A popular organised option is the 3-island tour (Ko Madsum + Ko Tean + one more island): departs 09:00-10:00, returns by 16:00, lunch included. Cost: 600-1,200 THB per person. For independent travel, rent a longtail boat from Ban Tai pier for 1,000-1,500 THB (up to 8 people). Best conditions are in the morning before wind picks up.

What to Bring

Mask, snorkel and fins are the essentials. Test the mask seal by pressing it to your face without the strap — it should hold by suction alone. Closed-heel fins are safer on rocky reefs. A thin 1-2 mm rash suit protects against sunburn and jellyfish. Apply anti-fog solution to the mask lens, spread evenly with a finger, then briefly rinse before entering the water.

Marine Life and Safety

Regular sightings near Ko Madsum and Ko Tean include clownfish, parrotfish, starfish, sea urchins, sea cucumbers and cuttlefish. Sea turtles are most commonly seen in Ang Thong. During October-February monitor beach warning flags for jellyfish. Never stand on coral or touch marine life — it damages the ecosystem and can cause injury.

Season and Visibility

Best visibility: January-September. The north-east monsoon (November-December) reduces clarity at east-coast beaches. The west coast (Na Thon, Lipa Noi) tends to be calmer during this period, making it a better option for snorkelling in the off-season.