Best Snorkeling in Koh Samui: Where to Go by Boat and From the Beach

Koh Samui is a beach island first and a reef destination second. Long, sandy bays like Chaweng and Lamai are great for swimming, but under you it is mostly sand, with only small patches of reef. The best snorkeling in Koh Samui is found in two kinds of places. There are the rocky coves on the island’s east coast, and there are the small islands offshore, which you reach by boat.

Below we go through both, say what each spot is like once you are in the water, and match them to how confident a swimmer you are and when you are travelling.

Quick facts

Best by boat	Koh Tan (Koh Taen), Koh Madsum (Pig Island), Ang Thong National Marine Park, plus Koh Nang Yuan near Koh Tao for a longer day
Best from the beach	Coral Cove and Silver Beach (Thong Takhian), both on the east coast between Chaweng and Lamai
Calmest, clearest months	Generally March to September; visibility drops in the October–December monsoon
Gear	Mask, snorkel and life jacket. Included on the Samui Journey catamaran. For the beach, bring or rent your own
Sunscreen rule	Oxybenzone, octinoxate, 4-MBC and butylparaben sunscreens are banned in Thailand’s marine national parks
Not a snorkel stop	The Five Islands (Koh Si Koh Ha), which you only see from the boat

Best snorkeling in Koh Samui by boat

Koh Tan (Koh Taen)

Koh Tan sits just off Samui’s south coast and often gets called Coral Island. Most Samui day trips stop here to snorkel, because the reefs are shallow, close to shore and fairly sheltered. You’ll see hard and soft corals, reef fish and, on a good day, the odd larger visitor. The popular spots get busy around midday, when a lot of tour boats arrive at once.

It is also the main swim stop on the Samui Journey 1-Day Catamaran, with snorkel gear, life jackets, kayaks, paddleboards and a floating sea pool on hand, all included in the price. Our Koh Tan snorkelling guide goes into the island and its reefs in more detail.

Koh Madsum (Pig Island)

Koh Madsum is next door to Koh Tan and best known for the pigs on its beach. The water is shallow, sandy and usually calm, good for a lazy swim but not much use for reef-watching. It’s where you cool off after the snorkel, not the main event.

Ang Thong National Marine Park

Ang Thong’s 42 limestone islands look dramatic from the surface. Underwater it is more mixed. The independent Thai National Parks guide notes average depths of around 10 metres, and visibility is often limited by sediment from the Tapi River on the mainland. Snorkelling is a pleasant part of an Ang Thong day, but people go for the viewpoint, the Emerald Lake and the kayaking. Torn between the two classic trips? Read Ang Thong or Pig Island.

Koh Nang Yuan and Koh Tao

Ask divers where the clear water is and many will point north, to Koh Tao and the three linked islets of Koh Nang Yuan. It costs you time. The crossing from Samui is much longer, so it makes for a full and tiring day. Koh Nang Yuan charges a separate entry fee, paid on arrival, and bans single-use plastic bottles on the island, so bring a reusable one.

What about the Five Islands?

Koh Si Koh Ha, off Samui’s south-west coast, is famous for its limestone towers and swiftlet nests, which are guarded against poachers. You look at it from the boat. It is not a snorkelling stop.

Snorkelling from the beach

You can see reef fish from Samui’s shore if you pick a rocky spot and a calm morning. The two best-known spots are both on the east coast between Chaweng and Lamai, along the coast road (Route 4169).

Coral Cove

A small cove framed by big boulders, with coral and fish close to shore. It’s small, so it fills up as the day goes on. Go early. You get in over sand and rocks, and water shoes help. Don’t count on a lifeguard at small coves like this. Stay within your comfort zone and watch for passing boats near the mouth of the cove.

Silver Beach (Thong Takhian)

Some guides call it Crystal Bay. It’s a short crescent of pale sand with rocks at each end. On calm days the water is often very clear, and the fish gather along the rocky edges. Families like it, and early morning is the quietest time.

When the east coast is rough

During the north-east monsoon, roughly October to December, waves and wind often hit the east coast. The west and south-west coasts tend to be more sheltered, but sheltered water doesn’t automatically mean reef. Ask locally before you go hunting for coral there.

Match the spot to your swimming level

When is the water clearest?

Visibility around Samui depends more on wind, swell and rain run-off than on the calendar. There is still a broad pattern.

• March to September: usually the calmest and clearest stretch. The Thai National Parks guide to Ang Thong points to March and April for clearer conditions.
• January and February: often good, though leftover monsoon swell can stir things up early in the year.
• October to December: the main rainy season on the Gulf side, with November the wettest month. Expect choppier seas, more cancelled boat trips and reduced visibility. Ang Thong usually closes from 1 November to 15 December.

Our best time to visit Koh Samui guide has a month-by-month breakdown.

Safety in the water

• Wear the life jacket if you are unsure. Nobody minds. It also lets you float flat and relaxed, which is how you see the most.
• Jellyfish: Thailand’s Department of Marine and Coastal Resources has warned of jellyfish around Koh Samui and Koh Pha Ngan, especially from July to December. Many beaches have an orange pole with vinegar and first-aid instructions. Rinse a sting with vinegar, not fresh water, and don’t rub it with sand.
• Boats: at beach spots, stay inside swimming areas and away from boat lanes. A brightly coloured rash guard or swim cap makes you easier to see.
• Sun: your back burns quickly while you float face down. A long-sleeved rash guard does more than any amount of sunscreen.
• Red flags and rain: do not snorkel when red flags are up, and avoid entering the sea right after heavy rain.

Reef etiquette

• Don’t stand on coral, even if it looks like rock. Find sand or float.
• Look, but don’t touch, chase or feed marine life.
• If you wear fins, keep them away from the reef. Kick gently and stay horizontal.
• Use reef-safe sunscreen. In Thailand’s marine national parks, sunscreens with oxybenzone, octinoxate, 4-MBC or butylparaben are banned, with fines of up to ฿100,000.
• Leave shells, coral and rocks where you found them.

Good to know

• First time with a snorkel? Practise at the surface next to the boat with a life jacket on, and breathe slowly through your mouth. The Koh Tan guide linked above covers mask fit and fogging step by step.
• Beach days need your own gear. For Coral Cove or Silver Beach, bring your own mask and snorkel or check what is available locally before you go.
• Go early, go calm. Mornings are usually quieter at the coves, and a flat, windless day matters more than the exact spot you choose.
• Plan a backup day: if the sea is too rough to swim, Samui Elephant Kingdom or the Explore the Real Samui 4×4 Island Safari still make a good day on land.
• Choosing a beach base: our guide to the best beaches in Koh Samui compares swimming conditions around the island.
• Packing: our guide to what to bring on a boat day covers swimwear, sun protection and dry bags.

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