Diving Thailand in December: Where to Go and What to Expect

Featured image: Weldon Kennedy from London, UK, CC BY 2.0, via Wikimedia Commons.

Diving Thailand in December: The Quick Verdict

The Andaman Sea is the safer December bet. Peak season there runs from November to April, and the Similan national park season runs from about October 15 to May 15. Park dates and closures are set by the Department of National Parks, so check its notices before paying a deposit. In the Gulf, Sail Rock's best whale shark window is March to May and October to early December. December is the tail end of that window, not the peak. Choose the Gulf for courses and Sail Rock, and keep your plans flexible. The table sums up each area.

Andaman Sea in December: Similan, Surin, Phuket, Phi Phi and Koh Lanta

The Similan Islands and Surin Islands hold Thailand's best-known sites. Richelieu Rock sits in the Surin group, and boats usually leave from Khao Lak or Ranong. Most liveaboards cover Similan and Surin on one trip. Koh Bon and Koh Tachai are the usual manta stops. Closer to shore, Phuket and Phi Phi operators run day trips throughout the year. Hin Daeng and Hin Muang lie inside Mu Koh Lanta National Park. Their season runs from November to April, so December is well inside it. Hin Daeng has Thailand's biggest vertical wall, plus caves and red and purple corals.

Gulf of Thailand in December: Koh Tao, Koh Phangan and Sail Rock

Koh Tao is the main Gulf base for learning to dive. Sail Rock (Hin Bai) sits between Koh Tao and Koh Phangan. The boat ride is about 1 hour from Koh Phangan and about 1.5 hours from Koh Tao or Koh Samui. The rock rises 8 m (26 ft) above the surface and drops to 40 m (130 ft). Divers can enter the 'chimney' at 5 m (16 ft) and exit at 18 m (60 ft). Gulf visibility is best from March to September, reaching up to 30 m (100 ft). December is outside that stretch, so expect less certainty. Ask your operator about sea state and visibility in the week you arrive.

Water Temperature, Visibility and Currents in December

Operators report 27–29°C (81–84°F) at the Similan and Surin Islands. Hin Daeng, Hin Muang and Sail Rock run 27–30°C (81–86°F). Our Thailand water temperature guide covers the monthly pattern. Visibility is usually good on the Andaman side but varies by site and day. Currents are the bigger planning issue. Richelieu Rock, Koh Bon and Koh Tachai can run medium to strong. At Koh Tachai, be ready to descend quickly to between 14 and 30 m (45 to 100 ft). Hin Daeng currents tend to be medium.

What You Can See in December

Treat big animals as possible, never promised. Richelieu Rock's whale shark window is February to April, so December is not its peak. Manta rays visit Koh Bon and Koh Tachai to feed and clean, and Hin Daeng sometimes gets one too. Gray reef sharks and leopard sharks show up often at Hin Daeng and Hin Muang. Sail Rock offers barracuda, trevally, longfin batfish and giant groupers. Early December can still produce whale sharks there. The Similan sites add swim-throughs, boulders and slopes, with plenty of reef fish.

Liveaboard, Day Trip or Island Base: Time, Cost and Access Trade-Offs

Liveaboards are the most direct way to reach Surin and the outer Similan sites. Trips of 3 nights are common, and the Surin Islands are reachable only by liveaboard. Day trips from Phuket or Khao Lak to the Similans are possible but long. Island bases such as Koh Lanta, Phi Phi and Koh Tao cut the travel time. From Phi Phi or Koh Lanta, Hin Daeng takes about 1.5 to 2 hours by boat. From Phuket, it is a full-day trip. Operators publish current Baht rates for each format, so compare two or three before booking.

Peak-Season Booking and Crowds

December falls inside the November-to-April peak, and Christmas and New Year add demand. Book flights, liveaboards and accommodation first, and add courses and day trips afterwards. Liveaboard berths on the Similan and Surin routes are the scarcest, so lock those in early. Richelieu Rock is usually very busy. Early morning or sunset dives are the best times to get in. Early December is typically calmer than the holiday window.

• Flights and accommodation: first, especially for Christmas week
• Liveaboard cabin: next, with the park season dates confirmed
• Courses and day trips: last, since island operators run them year round

Who Should Dive Thailand in December, and Who Should Pick Another Month

Advanced divers get the most from Richelieu Rock, Koh Bon and Koh Tachai. New divers and Open Water holders do better on Phuket and Phi Phi day trips, or on a Koh Tao course. If whale sharks are your main goal, February to April at Richelieu Rock is a better target. Always carry your own surface marker buoy and use it, even from an island base. Boat traffic and ascending divers have caused accidents. Check that your travel insurance covers diving.

• Booking a Similan trip without checking the park dates
• Diving without a surface marker buoy
• Expecting guaranteed whale sharks or mantas
• Skipping travel insurance with dive cover

Compare Nearby Months

November diving in Thailand is the start of the Andaman peak season. Seas are often calmer and boats less crowded. January diving in Thailand keeps the same west coast season and moves further from the Christmas rush. Sail Rock's whale shark window ends in early December, so late-season Gulf trips suit November better. Other months are linked below.

• February
• March
• April
• May
• June
• July
• August
• September
• October