Master Divers — Koh Tao Weekly Dive Report
Master Divers — Koh Tao Weekly Dive Report
Period: Monday 15.12 – Sunday 21.12
Location: Koh Tao, Gulf of Thailand
Mid-December continues to reflect typical northeast monsoon conditions in the Gulf of Thailand. Expect a mix of cloud cover, scattered rain and moderate to occasionally rough surface conditions. While diving remains possible throughout the week, planning will need to stay flexible as wind and sea state may change day to day.
☔ Rain Forecast
Scattered showers are likely throughout the week, consistent with TMD guidance for the lower Gulf during this period.
Rain is not expected to be constant, but passing showers may occur at any time of day, with a slightly higher chance mid- to late-week.
Some rain events may be heavier, especially when combined with stronger winds. These conditions can temporarily reduce surface visibility and affect entry and exit conditions at exposed sites.
For divers: morning dives are likely to offer the best chance for calmer surface conditions before wind or rain activity increases later in the day.
💨 Wind Conditions
Northeasterly winds will continue to dominate during this period.
Based on Windy and Windguru trends, wind speeds are expected to sit in the moderate range, with occasional stronger periods.
This wind direction can create choppier surface conditions on the eastern and northeastern sides of Koh Tao, while western and southwestern bays should remain more sheltered and suitable for diving.
Boat crossings may feel bumpy on windier days, and dive site selection should prioritize protection from wind and swell.
🌊 Swell & Waves
With the ongoing NE monsoon influence, moderate swell is expected through most of the week.
Wave heights are likely to range from approximately 1 to 2 meters, with short-period chop on top during stronger wind phases. Exposed east-facing sites may experience noticeable surge, particularly in shallower areas.
Dive strategy: sheltered sites on the west and southwest of the island will likely provide the best conditions, especially during windier days.
🌙 Tides & Currents
Koh Tao will continue to experience a standard semi-diurnal tidal pattern with two high and two low tides daily.
Stronger wind and swell may contribute to surface currents or localized surge, particularly around headlands or exposed reefs. Dive planning should remain flexible, and site selection should account for real-time sea behaviour.
👁️ Underwater Visibility
Visibility is expected to remain variable this week.
On calmer days and at protected or deeper sites, visibility may improve, while periods of rain, wind or swell can reduce clarity due to sediment movement and runoff.
As always, at Master Divers we select dive sites on a day-to-day basis to give you the best possible underwater conditions.
🐠 Marine Life Highlights
With some current and water movement in the area, there is a chance to encounter larger schooling fish such as barracudas, as well as rays moving along the reef edges.
At the same time, variable visibility makes this a great week to slow things down and focus on macro life. Keep an eye out for nudibranchs, shrimps, hermit crabs and other small reef residents tucked into protected areas.
🧭 Recommendations for Divers
Wetsuit:
Water temperatures remain warm at around 28 to 29 degrees Celsius. A 3 mm shorty or rashie is suitable for most divers, though those who get cold easily may prefer a full 3 mm suit.
Dive Timing:
Morning dives are recommended when conditions are often calmer.
Sheltered sites on the west and southwest side of the island are likely to provide the most consistent conditions this week.
Safety:
Be aware of changing surface conditions and follow your training.
Always listen to dive briefings and be prepared to adjust plans if wind or swell increases.
Dive safe and enjoy the underwater world. 🐬
We base our forecasts on Windguru, Windy.com, and guidance from the Thai Meteorological Department. Weather around Koh Tao can change quickly, so always check conditions locally before diving.
