Snorkelling on Koh Samui: where it's actually good

Is Koh Samui good for snorkelling?

Koh Samui is fine for an easy hour of snorkelling, but it is not a reef destination. If you have snorkelled the Red Sea or the Andaman coast, adjust your expectations. If this is your first time with a mask, or you have children with you, Samui's sheltered coves are a gentle place to start.

Most of Samui's coastline is sand, and the coral grows where granite boulders run into the sea, in small patches. Visibility varies a lot: a few metres after rain or a windy spell, noticeably better on a flat calm morning. Run-off after heavy rain clouds the water near shore for a day or two.

What you get in return is convenience. The best spots are a short drive from Chaweng and Lamai, the water is warm all year, and on a calm day you can be floating over coral within ten minutes of leaving the sand.

Koh Tao, Nang Yuan and Ang Thong: better reef, longer days

For coral and fish in numbers, the honest answer is Koh Tao and Koh Nang Yuan, with Ang Thong Marine Park a scenic second. Koh Tao has the best reefs within a day trip of Samui, and the three islets of Nang Yuan, joined by a sandbar, sit just off it. The trade-off is the crossing: roughly an hour and a half each way by speedboat, eight or nine hours door to door, on a busy boat. A common complaint about those days is more time in transit than in the water, and a rough ride home if the afternoon wind picks up.

If you have a calm forecast, a strong stomach and a spare full day, it is worth doing once. This Koh Tao and Nang Yuan snorkel tour is a straightforward way to do it. We do not go to Koh Tao ourselves; our slow wooden boat is not built for that crossing.

Ang Thong is about 40 limestone islands north-west of Samui. The snorkelling is decent rather than outstanding, and most people go for the scenery: the emerald lake on Koh Mae Ko and the viewpoint on Koh Wua Talab. Join-in day trips there run at roughly 1,200 to 2,000 baht a person (a rough market range), typically with 30 to 50 people on board and about an hour and a half each way by standard boat. The park is closed to visitors every year from 1 November to 15 December. Outside those dates, a Ang Thong day tour with kayaking, snorkelling and lunch covers it. More in Ang Thong or a small boat.

Where is the best snorkelling on Koh Samui itself?

The best snorkelling on Samui is on the east coast between Chaweng and Lamai, in the small boulder coves along the ring road. Two are worth your time.

Silver Beach (Crystal Bay). A small sandy cove closer to Lamai, with granite boulders at both ends. The coral and the fish are around those boulders, not in the middle of the bay, which is mostly sand. It is the easiest of the east-coast spots because you can walk in from the beach rather than climb down rocks. It also fills up from late morning. Our full Silver Beach guide covers getting there and when to go.

Coral Cove. A little further north, towards Chaweng Noi. It is smaller and rockier than Silver Beach, with less sand and a steeper way down from the road. The snorkelling around the rocks is similar, and because the beach is tiny it feels busy quickly.

The rocky coast either side of these coves is hard to reach from land, which is where a boat earns its keep. On the north coast, Bophut, Mae Nam and Bang Po are good for swimming, but the bottom is mostly sand and there is little to see with a mask.

Snorkelling from the shore or from a boat: what changes

The reef is the same either way; what changes is how you reach it.

From the shore, you find a patch of sand among the day visitors and swim out to the rocks. The awkward bits are entering over stone, the sea urchins wedged into gaps at shin height, and swimming back against a light chop when you are tired. Reef shoes help.

From a boat, you drop in where the water is already deep enough to float over the coral without kicking it, and climb out onto a deck with shade, a toilet and your bag. The catch is that the stop runs to the boat's timetable, not yours.

What will you actually see snorkelling on Samui?

Expect small reef fish in good numbers, boulder corals and a few branching patches, not a coral wall. On a decent day at Silver Beach you will see sergeant majors (the striped ones that come straight at your mask), parrotfish grazing the rock, butterflyfish, wrasse and shoals of small silver fish over the sand. Long-spined black sea urchins sit in the cracks between boulders, which is the main reason to keep your feet off the bottom.

Turtles and reef sharks are possible around Koh Tao. On Samui's shore reefs they are rare enough that we would never promise either. If someone sells you a Samui snorkelling trip on the strength of turtles, ask where they last saw one.

When is the water clearest around Koh Samui?

The calmest seas and clearest water are usually from late December to April, and again from June to August. Samui's weather runs opposite to Phuket's: when the Andaman coast has its wet season, roughly May to October, Samui is usually at its best.

Mid-October to mid-December is the north-east monsoon here. It is the wettest, windiest stretch of the year, and the east coast, where Silver Beach and Coral Cove are, takes the swell first. The north coast is sometimes easier, but a strong north-easterly makes it rough too; the crew decide on the day. Snorkelling in that window is a gamble: some mornings are flat and fine, others are churned up and murky. Rain tends to come in bursts with sunny spells between, rather than all day, and the seas settle from late December. More on that in our guide to the Koh Samui rainy season.

Time of day matters as much as month. Mornings are usually calmer, before the wind gets up, and the coves are quieter before the midday crowd arrives.

What to bring, and how not to damage the reef

Bring a mask that fits, sun protection you can swim in, and the habit of never standing on coral.

• Reef-safe sunscreen. Thailand has banned sunscreens containing oxybenzone, octinoxate and a few related chemicals in its marine national parks since 2021. It is a good rule everywhere. Put it on half an hour before you get in.
• A rash vest. Better than sunscreen for your back, which is all the sun sees while you float face down. It also reduces the skin exposed to jellyfish. Jellyfish, including dangerous box jellyfish, do occur in the Gulf of Thailand, so swim where the crew say and wear cover-ups.
• Reef shoes if you are going in from the shore over rocks.
• A mask that seals. Test it before you swim: press it to your face without the strap and breathe in through your nose. If it stays put, it fits. A dab of baby shampoo stops it fogging.
• Hands and feet off the coral. Don't stand on it, don't touch it, don't feed the fish. If you need a rest, float on your back or head for the sand.

For children, a snorkel vest or lifejacket matters more than any of the above. Even strong young swimmers tire quickly with their face in the water, and a vest lets them float and look without effort. Our boat trips with kids guide covers the rest.

How our half-day trip does it

Our half-day trip is a slow morning on a traditional Thai teak cruiser with a snorkelling stop at Silver Beach or Coral Cove, not a reef expedition. We board at 09:00 at Petcharat Marina in Bangrak or Hansar Samui Resort in Bophut, cruise north along the Big Buddha coast past Koh Faan, then round to the east coast and anchor off Silver Beach or Coral Cove next door, whichever suits the group and the sea that day. The crew adjust the route for the sea on the day, and sometimes use the neighbouring coves when conditions favour them.

Snorkelling gear is there for every guest. Children aged 4 to 11 get a supervised snorkelling session with the crew in shallow water. It is recreational and patient, not certified instruction. Anyone who would rather not put their face in the water can lie on the double floating beanbags, jump off the roof, or take the dinghy ashore for some time on the sand. Lunch is served on board and we are back alongside by 14:00.

One family put it simply on Google: "This was a particular highlight for the children: snorkeling, swimming, and jumping into the sea from the roof of the boat." That is the level to expect: an easy snorkel with everything on the boat, not the best reef in Thailand.

The half-day trip runs Monday to Friday, for up to 15 guests, at ฿2,900 per adult and ฿1,900 per child aged 4 to 11. If you want the boat to yourselves, a private charter lets you plan the stops with the crew and ask for an early start, so you can be in the water before the coves get busy.

Who it doesn't suit: experienced snorkellers chasing coral walls and turtles. Go to Koh Tao on a calm day. And it is never a party boat.