{
  "destination": "thailand",
  "name": "Thailand",
  "question": "Can you snorkel and dive from a charter boat in Thailand, and how warm is the sea?",
  "answer": "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.",
  "canonical_url": "https://catamaranindex.com/snorkel-dive/thailand/",
  "markdown_url": "https://catamaranindex.com/snorkel-dive/thailand.md",
  "destination_url": "https://catamaranindex.com/thailand/",
  "best_time_url": "https://catamaranindex.com/best-time/thailand/",
  "fishing_url": "https://catamaranindex.com/fishing/thailand/",
  "api_url": "https://catamaranindex.com/api/snorkel-dive/thailand.json",
  "book_url": "https://catamaranindex.com/go/samboat?dest=thailand&pos=api",
  "checked": "2026-10-28",
  "sea_temperature": {
    "unit": "celsius",
    "source": "NOAA OISST v2.1 long-term monthly mean",
    "period": "1991–2020",
    "reference_point": {
      "place": "Andaman Sea south of Phuket",
      "lat": 7.625,
      "lon": 98.375
    },
    "note": "NOAA OISST v2.1 long-term mean, 1991–2020, one 1/4° sea cell per destination. It is the sea surface; shallow bays can be warmer and water at depth cooler.",
    "warm_water_threshold_c": 24,
    "months": [
      {
        "month": 1,
        "name": "January",
        "sea_c": 28.4,
        "warm_water": true,
        "wetsuit_rule_of_thumb": "swimsuit or rash vest"
      },
      {
        "month": 2,
        "name": "February",
        "sea_c": 28.7,
        "warm_water": true,
        "wetsuit_rule_of_thumb": "swimsuit or rash vest"
      },
      {
        "month": 3,
        "name": "March",
        "sea_c": 29.3,
        "warm_water": true,
        "wetsuit_rule_of_thumb": "swimsuit or rash vest"
      },
      {
        "month": 4,
        "name": "April",
        "sea_c": 29.9,
        "warm_water": true,
        "wetsuit_rule_of_thumb": "swimsuit or rash vest"
      },
      {
        "month": 5,
        "name": "May",
        "sea_c": 30,
        "warm_water": true,
        "wetsuit_rule_of_thumb": "swimsuit or rash vest"
      },
      {
        "month": 6,
        "name": "June",
        "sea_c": 29.8,
        "warm_water": true,
        "wetsuit_rule_of_thumb": "swimsuit or rash vest"
      },
      {
        "month": 7,
        "name": "July",
        "sea_c": 29.6,
        "warm_water": true,
        "wetsuit_rule_of_thumb": "swimsuit or rash vest"
      },
      {
        "month": 8,
        "name": "August",
        "sea_c": 29.5,
        "warm_water": true,
        "wetsuit_rule_of_thumb": "swimsuit or rash vest"
      },
      {
        "month": 9,
        "name": "September",
        "sea_c": 29,
        "warm_water": true,
        "wetsuit_rule_of_thumb": "swimsuit or rash vest"
      },
      {
        "month": 10,
        "name": "October",
        "sea_c": 28.8,
        "warm_water": true,
        "wetsuit_rule_of_thumb": "swimsuit or rash vest"
      },
      {
        "month": 11,
        "name": "November",
        "sea_c": 28.8,
        "warm_water": true,
        "wetsuit_rule_of_thumb": "swimsuit or rash vest"
      },
      {
        "month": 12,
        "name": "December",
        "sea_c": 28.6,
        "warm_water": true,
        "wetsuit_rule_of_thumb": "swimsuit or rash vest"
      }
    ],
    "derived": "warm_water and wetsuit_rule_of_thumb are our rules applied to the NOAA mean; sea_c is NOAA's, rounded to 0.1."
  },
  "wetsuit_rule": "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.",
  "sites": [
    {
      "name": "Mu Ko Similan National Park",
      "kind": "national park",
      "where": "Andaman Sea, north-west of Phuket",
      "facts": [
        {
          "text": "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.",
          "status": "secondary",
          "sources": [
            {
              "id": "dive_th_thairath",
              "name": "Thairath (newspaper)",
              "title": "Similan and Surin close for five months",
              "url": "https://en.thairath.co.th/news/local/2932885",
              "checked": "2026-10-28",
              "note": "News report dated 15 May 2026 on the Department of National Parks (DNP) closure announcement; we did not find the DNP notice itself.",
              "tier": "secondary"
            },
            {
              "id": "dive_th_aster",
              "name": "Aster of Asia (tour operator)",
              "title": "Similan Islands 2026: opening on 15 October",
              "url": "https://asterofasia.com/blog/similan-islands-2026-season-opening",
              "checked": "2026-10-28",
              "note": "Tour operator blog dated 16 October 2026; it says it was AI-assisted and human-checked. Not official.",
              "tier": "secondary"
            }
          ]
        },
        {
          "text": "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.",
          "status": "secondary",
          "sources": [
            {
              "id": "fish_thailand_1",
              "name": "Thai Marine Guide",
              "title": "Thai Marine Guide – restricted areas",
              "url": "https://thaimarineguide.com/info/restricted-areas/",
              "checked": "2026-10-28",
              "note": "Secondary source (not official).",
              "tier": "secondary"
            }
          ]
        }
      ]
    },
    {
      "name": "Mu Ko Surin National Park",
      "kind": "national park",
      "where": "Andaman Sea, north of the Similans",
      "facts": [
        {
          "text": "Thairath reported that Surin's tourism areas close in the same period as the Similans.",
          "status": "secondary",
          "sources": [
            {
              "id": "dive_th_thairath",
              "name": "Thairath (newspaper)",
              "title": "Similan and Surin close for five months",
              "url": "https://en.thairath.co.th/news/local/2932885",
              "checked": "2026-10-28",
              "note": "News report dated 15 May 2026 on the Department of National Parks (DNP) closure announcement; we did not find the DNP notice itself.",
              "tier": "secondary"
            }
          ]
        }
      ]
    }
  ],
  "fees": [
    {
      "item": "Similan entrance fee, foreign adult",
      "amount": "500 THB",
      "status": "secondary",
      "note": "Tour operator blog; it says the rate has applied since 7 June 2022. Children: 250 THB.",
      "sources": [
        {
          "id": "dive_th_aster",
          "name": "Aster of Asia (tour operator)",
          "title": "Similan Islands 2026: opening on 15 October",
          "url": "https://asterofasia.com/blog/similan-islands-2026-season-opening",
          "checked": "2026-10-28",
          "note": "Tour operator blog dated 16 October 2026; it says it was AI-assisted and human-checked. Not official.",
          "tier": "secondary"
        }
      ]
    },
    {
      "item": "Anchoring fees in marine national parks",
      "amount": "Not verified",
      "status": "not_verified",
      "note": "Thai Marine Guide says rangers can charge anchoring fees set by the department, by yacht size and people on board.",
      "sources": [
        {
          "id": "fish_thailand_1",
          "name": "Thai Marine Guide",
          "title": "Thai Marine Guide – restricted areas",
          "url": "https://thaimarineguide.com/info/restricted-areas/",
          "checked": "2026-10-28",
          "note": "Secondary source (not official).",
          "tier": "secondary"
        }
      ]
    }
  ],
  "mooring_and_anchoring": [
    {
      "text": "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.",
      "status": "secondary",
      "sources": [
        {
          "id": "fish_thailand_1",
          "name": "Thai Marine Guide",
          "title": "Thai Marine Guide – restricted areas",
          "url": "https://thaimarineguide.com/info/restricted-areas/",
          "checked": "2026-10-28",
          "note": "Secondary source (not official).",
          "tier": "secondary"
        }
      ]
    },
    {
      "text": "Similan: no anchoring at islands 1–3 (Thai Marine Guide).",
      "status": "secondary",
      "sources": [
        {
          "id": "fish_thailand_1",
          "name": "Thai Marine Guide",
          "title": "Thai Marine Guide – restricted areas",
          "url": "https://thaimarineguide.com/info/restricted-areas/",
          "checked": "2026-10-28",
          "note": "Secondary source (not official).",
          "tier": "secondary"
        }
      ]
    }
  ],
  "diving": [
    {
      "text": "Similan: overnight stays on a private yacht only with diving equipment and a dive certification on board (Thai Marine Guide).",
      "status": "secondary",
      "sources": [
        {
          "id": "fish_thailand_1",
          "name": "Thai Marine Guide",
          "title": "Thai Marine Guide – restricted areas",
          "url": "https://thaimarineguide.com/info/restricted-areas/",
          "checked": "2026-10-28",
          "note": "Secondary source (not official).",
          "tier": "secondary"
        }
      ]
    },
    {
      "text": "Whether visitors must dive with a licensed operator in Thai marine parks: not verified.",
      "status": "not_verified",
      "sources": []
    }
  ],
  "visibility": {
    "text": "We found no official or survey source for underwater visibility, so we give no figure. Ask the local dive centre on the day.",
    "status": "not_verified",
    "sources": []
  },
  "not_verified": [
    "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."
  ],
  "source_counts": {
    "official": 1,
    "secondary": 3
  },
  "status_legend": {
    "official": "Read in an official text: government, park authority, ministry or official tourism board.",
    "secondary": "From a newspaper, NGO, guide or tour operator; not official.",
    "not_verified": "We could not confirm it. We leave it open rather than guess."
  },
  "caveat": "Park rules change and some are seasonal. Check with the park, the charter base or a local dive centre. The answer, wetsuit column and warm-water flag are our wording and rules applied to labelled facts and NOAA means.",
  "sources": [
    {
      "id": "dive_th_thairath",
      "name": "Thairath (newspaper)",
      "title": "Similan and Surin close for five months",
      "url": "https://en.thairath.co.th/news/local/2932885",
      "checked": "2026-10-28",
      "note": "News report dated 15 May 2026 on the Department of National Parks (DNP) closure announcement; we did not find the DNP notice itself.",
      "tier": "secondary"
    },
    {
      "id": "dive_th_aster",
      "name": "Aster of Asia (tour operator)",
      "title": "Similan Islands 2026: opening on 15 October",
      "url": "https://asterofasia.com/blog/similan-islands-2026-season-opening",
      "checked": "2026-10-28",
      "note": "Tour operator blog dated 16 October 2026; it says it was AI-assisted and human-checked. Not official.",
      "tier": "secondary"
    },
    {
      "id": "fish_thailand_1",
      "name": "Thai Marine Guide",
      "title": "Thai Marine Guide – restricted areas",
      "url": "https://thaimarineguide.com/info/restricted-areas/",
      "checked": "2026-10-28",
      "note": "Secondary source (not official).",
      "tier": "secondary"
    },
    {
      "id": "noaa_oisst_ltm",
      "name": "NOAA PSL (NOAA/NCEI OISST v2.1)",
      "title": "NOAA High-resolution Blended Analysis: OISST v2.1 long-term mean monthly sea surface temperature, 1991–2020 (sst.mon.ltm.1991-2020.nc)",
      "url": "https://psl.noaa.gov/thredds/catalog/Datasets/noaa.oisst.v2.highres/catalog.html",
      "checked": "2026-10-28",
      "note": "NOAA's published 1/4° monthly climatology (climo_period 1991/01/01–2020/12/31; every month of every cell we use rests on 30 years). Read on 28 Oct 2026 through PSL's THREDDS point service by scripts/fetch-sst.mjs; we chose one sea cell per destination and rounded to 0.1 °C. Satellite-and-in-situ analysis of the sea surface, not a beach or depth reading.",
      "tier": "official"
    }
  ],
  "attribution": "Cite \"Catamaran Index\" with a link to the canonical_url of the page the figure comes from, and name the original source listed with it.",
  "affiliate_note": "book_url links go through /go/samboat, an affiliate link: Catamaran Index may earn a commission on bookings, at no extra cost to the traveller. It never changes the data."
}