Marine & ocean
Samui's own shore reefs are pretty rather than spectacular; the clearest water is on the islands around it. Sea conditions change with the season — the calmest months are usually February to September.
Updated 14 Nov 2026
Advisory: Rough sea forecast for the lower Gulf, 15 Nov: waves 2 m (TMD)
Rough sea forecast (TMD): speedboats, snorkel and island trips may be cancelled; car ferries usually run but can be delayed. This is not an operator cancellation.
Source: Thai Meteorological Department (TMD)Checked 14 Nov 2026, 21:07 ICTValid until 16 Nov 2026, 00:00
Ang Thong closure: Seasonal closure usually starts 1 November; 2026 reopening date not yet confirmed (sources say 30 Nov – 23 Dec). Check with the park before booking.
Park informationChecked 10 Nov 2026
Sea today
Rough sea forecast
Speedboats, snorkel and island trips may be cancelled; car ferries usually run but can be delayed. This is not an operator cancellation: confirm with your operator.
Lower: Easterly winds 11-18 knots or 20-35 km./hr. Wave height about 2 meters and above 2 meters in thundershowers.
Issued 15 Nov 2026, 00:00 · fetched 00:07 · TMD shipping forecast
The main snorkel stop of south-coast boat trips, with corals and reef fish close to the beach.
How to get there: Longtail boat from Thong Krut pier on the south coast — a short crossing, often combined with Koh Madsum.
checked 7 Nov 2026
An archipelago of 42 islands. Snorkelling is best around the northern islands; the park fee may not be included in tour prices.
How to get there: Only with licensed tour operators (group boat tours or private charter) from Samui's piers.
Often called the clearest reef within day-trip reach. The island is privately run and charges a landing fee (amounts vary — check locally).
How to get there: Full-day speedboat tours from Samui — a long open-water crossing, weather-dependent.
checked 7 Nov 2026
Granite boulders and shallow coral close to shore — beginner-friendly in calm conditions. East coast: rough in the northeast monsoon.
How to get there: Shore entry from the small cove off the ring road between Chaweng Noi and Lamai.
Reef fish around the rocks on calm days. East coast: check the sea state from October to December.
How to get there: Shore entry; snorkel along the boulders at both ends of the bay.
Place detailschecked 7 Nov 2026
Officials have warned of venomous box jellyfish around Samui and Koh Phangan, mainly from about July to December. Swim in netted areas where available. If stung: pour household vinegar on the sting for at least 30 seconds — no fresh water, ice, sand or rubbing — and get medical help (emergency 1669).
SourceVinegar posts exist on some beaches, but many have been found empty or missing. Carrying a small bottle is the safe option.
SourceEast-coast beaches such as Chaweng and Lamai are most dangerous in the northeast monsoon. Lifeguards are not everywhere. Caught in a rip current: don't fight it — float, raise an arm and swim parallel to the shore.
SourceThailand bans sunscreens with oxybenzone, octinoxate, 4-MBC or butylparaben in all marine national parks, including Ang Thong (fines up to 100,000 THB). Use mineral sunscreen or a rash guard.
SourceDon't stand on or touch coral, don't feed fish, take your rubbish back. Many day-trip islands ban plastic bottles.
