Snorkelling and diving from a charter boat in Thailand
Thailand: snorkel and dive sites by boat, park fees, anchoring rules, sea temperature by month (NOAA) and wetsuit advice. Sourced.
Sea temperature
28.4–30.0 °C
January to May, NOAA 1991–2020
Source: NOAA PSL (NOAA/NCEI OISST v2.1), checked
Warm water (≥24 °C)
All year
Our threshold on NOAA means
Park fee
500 THB
Similan entrance fee, foreign adult (secondary)
Source: Aster of Asia (tour operator), checked
Checked
28 Oct 2026
1 official, 3 secondary
Yes, in season: the Similan and Surin national parks closed from 16 May to 15 October 2026, and Similan islands 1–3 are closed to anchoring, snorkelling and diving, according to news and guide sources (we found no official Thai page). The sea averages between 28.4 °C (January) and 30.0 °C (May) by NOAA's 1991–2020 means at our reference point, so it stays at 24 °C or more all year and by our rule of thumb a swimsuit or rash vest is enough even in the coolest month.
Checked 28 Oct 2026 against 1 official and 3 secondary sources; sea temperature from NOAA (sources). Anything we could not confirm is labelled (how to read the labels). Park rules change: check before you go.
Snorkel and dive sites you can reach by charter boat in Thailand
| Site | Type | Where | What the source says |
|---|---|---|---|
| Mu Ko Similan National Park | national park | Andaman Sea, north-west of Phuket | [Secondary source] Thairath reported that the Department of National Parks closed the park from 16 May to 15 October 2026; Aster of Asia, a tour operator, says the 2026–27 season runs from 15 October 2026 to 15 May 2027. (Thairath (newspaper); Aster of Asia (tour operator)) [Secondary source] Thai Marine Guide says private yachts need a permit from the park headquarters before entering, may stay overnight only with diving equipment and a dive certification on board, and that anchoring, landing, snorkelling and diving are prohibited at islands 1–3. (Thai Marine Guide) |
| Mu Ko Surin National Park | national park | Andaman Sea, north of the Similans | [Secondary source] Thairath reported that Surin's tourism areas close in the same period as the Similans. (Thairath (newspaper)) |
These are the sites we could document from official or labelled sources, not a full list. Fishing is a separate question: fishing rules in Thailand.
Sea temperature in Thailand by month
The sea is warmest in May (30.0 °C) and coolest in January (28.4 °C). ● marks our warm-water months (24 °C or more): all year.
| Month | Sea surface (NOAA) | Air (NASA POWER) | Our wetsuit rule of thumb | Catamaran, avg per week (12 Knots) |
|---|---|---|---|---|
| January | 28.4 °C ● | 27.2 °C | swimsuit or rash vest | €10,235 |
| February | 28.7 °C ● | 27.7 °C | swimsuit or rash vest | €9,938 |
| March | 29.3 °C ● | 28.7 °C | swimsuit or rash vest | €9,125 |
| April | 29.9 °C ● | 29.0 °C | swimsuit or rash vest | €8,165 |
| May | 30.0 °C ● | 28.9 °C | swimsuit or rash vest | €5,324 |
| June | 29.8 °C ● | 28.4 °C | swimsuit or rash vest | €5,062 |
| July | 29.6 °C ● | 28.2 °C | swimsuit or rash vest | €5,073 |
| August | 29.5 °C ● | 28.0 °C | swimsuit or rash vest | €4,996 |
| September | 29.0 °C ● | 27.7 °C | swimsuit or rash vest | €5,016 |
| October | 28.8 °C ● | 27.5 °C | swimsuit or rash vest | €6,671 |
| November | 28.8 °C ● | 27.6 °C | swimsuit or rash vest | €9,397 |
| December | 28.6 °C ● | 27.3 °C | swimsuit or rash vest | €10,140 |
Of the twelve months (all at 24 °C or more), the cheapest on 12 Knots' average weekly catamaran price is August at €4,996 per week (12 Knots, checked 27 Oct 2026), with the sea at 29.5 °C (our comparison).
Sea surface: NOAA OISST v2.1 1991–2020 monthly mean for the 1/4° cell centred on 7.625° N, 98.375° E (Andaman Sea south of Phuket) (NOAA PSL (NOAA/NCEI OISST v2.1), checked 28 Oct 2026); the sites above may be warmer or cooler, and shallow bays warm up faster. Air: our 10-year NASA POWER mean at Ao Chalong, Phuket (NASA POWER, checked 28 Oct 2026). Prices are asking prices that mix bareboat and crewed listings.
Mooring, anchoring and park rules for your boat
- [Secondary source] Thai Marine Guide: most anchorages have mooring buoys (yellow or red with a blue band); if none is free, anchor well away from coral, because damaging coral is a criminal offence. (Thai Marine Guide)
- [Secondary source] Similan: no anchoring at islands 1–3 (Thai Marine Guide). (Thai Marine Guide)
Can I scuba dive from the boat? Permits and dive centres
- [Secondary source] Similan: overnight stays on a private yacht only with diving equipment and a dive certification on board (Thai Marine Guide). (Thai Marine Guide)
- [Not verified] Whether visitors must dive with a licensed operator in Thai marine parks: not verified.
Park and mooring fees
| Fee | Amount | Status | Source |
|---|---|---|---|
| Similan entrance fee, foreign adult | 500 THB (Tour operator blog; it says the rate has applied since 7 June 2022. Children: 250 THB.) | secondary | Aster of Asia (tour operator) |
| Anchoring fees in marine national parks | Not verified (Thai Marine Guide says rangers can charge anchoring fees set by the department, by yacht size and people on board.) | not verified | Thai Marine Guide |
Underwater visibility
[Not verified] We found no official or survey source for underwater visibility, so we give no figure. Ask the local dive centre on the day.
What wetsuit do I need in Thailand?
From May's 30.0 °C our rule of thumb gives a swimsuit or rash vest; in January (28.4 °C) a swimsuit or rash vest. The month-by-month column is in the table above.
Our rule of thumb for snorkelling, applied to the monthly mean: 28 °C or more: swimsuit or rash vest; 26–28 °C: rash vest or 1–2 mm shorty; 24–26 °C: 3 mm shorty; 21–24 °C: 3 mm full wetsuit; 18–21 °C: 5 mm full wetsuit; below 18 °C: 7 mm wetsuit, or a drysuit for diving. Divers lose heat faster and meet cooler water at depth: go one band thicker. People feel cold differently; this is a guide, not a source's advice.
| Mean sea temperature | Our rule of thumb for snorkelling |
|---|---|
| 28 °C or more | swimsuit or rash vest |
| 26–28 °C | rash vest or 1–2 mm shorty |
| 24–26 °C | 3 mm shorty |
| 21–24 °C | 3 mm full wetsuit |
| 18–21 °C | 5 mm full wetsuit |
| Below 18 °C | 7 mm wetsuit, or a drysuit for diving |
See boats in Thailand
See catamarans for rent in Thailand on SamBoat
Check the park rules above and the boat's own kit (snorkel gear, dinghy, dive-ladder) with the operator before you book; listings and prices on SamBoat are SamBoat's own. We may earn a commission if you book through our links, at no extra cost to you (disclosure).
What we could not verify
- The Department of National Parks' own closure notice and fee schedule (we read news and operator reports).
- The yacht permit process and its cost at Similan.
- Rules at Phi Phi and in Phang Nga Bay.
- Underwater visibility.
How to read the labels
- [Secondary source]: From a newspaper, NGO, guide or tour operator; not official.
- [Not verified]: We could not confirm it. We leave it open rather than guess.
- No label: Read in an official text: government, park authority, ministry or official tourism board.
Sea temperatures are NOAA's; the wetsuit column, the 24 °C warm-water mark and any sum or comparison are ours and say so. Park rules change and some are seasonal: check with the park, your charter base or a local dive centre before you go.
Sources
- Thairath (newspaper): Similan and Surin close for five months (secondary, not official), checked 28 Oct 2026.
- Aster of Asia (tour operator): Similan Islands 2026: opening on 15 October (secondary, not official), checked 28 Oct 2026.
- Thai Marine Guide: Thai Marine Guide – restricted areas (secondary, not official), checked 28 Oct 2026.
- NOAA PSL (NOAA/NCEI OISST v2.1): NOAA High-resolution Blended Analysis: OISST v2.1 long-term mean monthly sea surface temperature, 1991–2020 (sst.mon.ltm.1991-2020.nc) (official), checked 28 Oct 2026.
- NASA POWER: Prediction Of Worldwide Energy Resources: Monthly API (T2M, WS10M) (official), air temperature, pulled 28 Oct 2026.
- 12 Knots: Catamaran charter in Thailand (secondary, prices), checked 27 Oct 2026.
Method: methodology. Data: JSON.
More on Thailand
Frequently asked questions
Can you snorkel and dive from a charter boat in Thailand?
Yes, in season: the Similan and Surin national parks closed from 16 May to 15 October 2026, and Similan islands 1–3 are closed to anchoring, snorkelling and diving, according to news and guide sources (we found no official Thai page). The sea averages between 28.4 °C (January) and 30.0 °C (May) by NOAA's 1991–2020 means at our reference point, so it stays at 24 °C or more all year and by our rule of thumb a swimsuit or rash vest is enough even in the coolest month.
How warm is the sea in Thailand?
By NOAA's 1991–2020 averages at our reference point (Andaman Sea south of Phuket), the sea surface is warmest in May at 30.0 °C and coolest in January at 28.4 °C. Months at 24 °C or more: all year.
Do I need a wetsuit to snorkel in Thailand?
By our rule of thumb (not a source's advice): a swimsuit or rash vest in May and a swimsuit or rash vest in January; divers should go one band thicker.
Do I need a dive centre to scuba dive in Thailand?
Secondary source: Similan: overnight stays on a private yacht only with diving equipment and a dive certification on board (Thai Marine Guide). Not verified: Whether visitors must dive with a licensed operator in Thai marine parks: not verified.
Are there park fees or mooring rules for boats in Thailand?
Secondary source: Thai Marine Guide: most anchorages have mooring buoys (yellow or red with a blue band); if none is free, anchor well away from coral, because damaging coral is a criminal offence. Secondary source: Similan: no anchoring at islands 1–3 (Thai Marine Guide). Fees: Similan entrance fee, foreign adult: 500 THB (secondary source).