Master Divers — Koh Tao Dive Report 01.12 – 07.12
Period: Monday 1.12 – Sunday 7.12
Location: Koh Tao, Gulf of Thailand
Koh Tao Dive Report 01.12 – 07.12
Early December marks the height of the northeast monsoon, and next week is expected to reflect this seasonal pattern. Koh Tao will likely see a combination of fresh winds, passing rain, and moderate to rough sea conditions across several days. Dive operations should expect some variability and prepare for potential limits on exposed sites.
☔ Rain Forecast
Based on outlooks for the upper Gulf, isolated to scattered rain is expected throughout the week, with an increased chance of heavier showers around midweek. Some thundershower activity is possible during periods of stronger wind.
Rainfall will likely occur in short but intense bursts rather than all-day rain. Morning hours may still offer better chances for calmer surface conditions before winds rise during the afternoon.
Rain alone does not usually affect diving, but rain combined with swell and wind can decrease visibility and create more movement on the surface. Planning morning dives is advisable.
💨 Wind Conditions
Windguru and Windy both show continued northeast winds through the week.
Typical speeds for early December are forecast around 15–25 knots, occasionally higher during passing showers or offshore gusts.
The northeasterly direction means the east and northeast sides of Koh Tao will be more exposed to chop and surface disturbance. The western and southwestern bays will remain the most sheltered options.
As winds increase midday into the afternoon, surface conditions can become uncomfortable during entries and exits. Anticipate limited access to exposed sites later in the week.
🌊 Swell and Waves
Wave height across the Gulf is expected to be moderate, generally around 1.0–2.0 meters throughout the week, with potential for higher waves during potential thundershowers. The swell direction remains primarily from the northeast, matching the monsoon wind.
Surge is likely at shallow and east-facing reef areas, especially during stronger wind days. Protected sites in the southwest, such as Japanese Gardens, Twins, and Mango Bay, may offer calmer conditions.
Choose sheltered sites and avoid surge-prone areas when winds pick up. Boats may need to use alternate mooring areas to minimize surface risk.
🌙 Tides and Currents
Regular twice-daily highs and lows will continue. Stronger wind across several days may contribute to surface currents or added surge at depth, particularly during the early afternoon.
Currents may be more noticeable around pinnacles or outer reef structures. Dive leaders should check real-time currents before final site selection.
👁️ Underwater Visibility
With ongoing wind and intermittent rain, visibility will remain on the lower side for much of the week. Expect 2–6 meters depending on location and timing, with the best conditions likely on the western side of the island.
Heavier rain or rougher swell can temporarily drop visibility even further due to suspended sediment.
Morning dives and deeper sites may provide more stable conditions. As always, Master Divers select sites daily to give you the best underwater experience possible.
🐠 Marine Life Highlights
Challenging conditions often bring exciting sightings. With currents at times present, this can be a good week for observing larger pelagic visitors such as barracudas and rays, including blue spotted stingrays resting in sandy patches.
Reduced visibility also makes it an ideal time to focus on macro life. Expect to find nudibranchs, shrimps, hermit crabs, and other small reef dwellers sheltering from the surge.
🧭 Recommendations for Divers
Wetsuit: Sea temperature remains around 28–29°C, so a 3 mm shorty or rash guard is generally enough. If you get cold easily or expect multiple dives, a full 3 mm can help.
Timing:
• Plan for early morning dives whenever possible.
• Afternoon trips may encounter stronger winds and surface movement.
Safety:
• Follow boat crew instructions closely during choppy conditions.
• Use proper surface signaling and maintain contact with your buddy during low visibility.
• Dive within your limits and choose conservative profiles when conditions fluctuate.
Dive safe and enjoy your week underwater! 🐬
We base our forecasts on Windguru, Windy.com, and TMD guidance, but with Koh Tao’s rapidly changing weather, conditions can shift quickly. Always verify local conditions before diving.
