If you are dreaming of vibrant coral reefs, massive granite boulders, and swimming alongside the ocean’s gentle giants, the Andaman coast is calling. However, because this region is highly protected, understanding the Khao Lak diving season is the most important step in planning your trip.
Khao Lak serves as the premier gateway to the world-renowned Similan and Surin Islands. To preserve these delicate marine ecosystems and ensure diver safety during monsoon months, the Thai government strictly regulates when boats can enter the marine parks.
Here is your ultimate guide to the seasons, weather, and marine life you can expect when diving in Khao Lak.
The Official Similan Islands Diving Season Dates
The official Khao Lak diving season when the Similan Islands and Surin Islands (including Richelieu Rock) are open to the public runs from October 15th to May 15th every year.
Outside of these dates, the national parks are closed. During the open season, however, the underwater conditions change from month to month. Here is what you need to know to time your trip perfectly.
Month-by-Month Breakdown of the Khao Lak Diving Season
November to December: Crystal Clear Beginnings
As the monsoon winds die down, the diving season opens with some of the best visibility of the year. During November and December, the water is incredibly clear, often offering visibility of 30 meters or more. The water temperature is slightly cooler (around 27°C to 28°C), making it a fantastic time for underwater photography, macro spotting, and exploring the pristine topography of the Similan Islands before the peak holiday crowds arrive.
January to February: Flat Seas and Perfect Crossings
January and February mark the sweet spot for weather. The skies are generally cloudless, and the Andaman Sea becomes as flat as glass. If you are prone to seasickness, this is the best time to book a liveaboard. The shifting nutrient-rich currents during this period also signal the beginning of Manta Ray sightings, particularly around the cleaning stations of Koh Bon and Koh Tachai.
March to April: The Season of the Giants (Peak Season)
If your ultimate goal is to see a Whale Shark, this is the time to be here. As the water temperature warms up (often reaching 29°C to 30°C), natural plankton blooms occur. While this slightly reduces water clarity, it creates an all-you-can-eat buffet for large pelagics.
March and April are world-famous for consistent Whale Shark and Manta Ray encounters, especially at Richelieu Rock. Because this window is highly sought after by divers worldwide, trips book up incredibly fast.
May: The Quiet Finale
The first two weeks of May offer a unique, off-the-beaten-path experience. The crowds thin out dramatically just before the parks close on May 15th. While the weather can be a bit more unpredictable as the season transitions, you will often find yourself diving some of Thailand’s best sites with almost no other boats around.
June to October: The “Green” Season
From mid-May to mid-October, the marine parks are closed to allow the reefs to recover. While you cannot visit the Similans, diving doesn’t stop entirely. Local coastal dive sites, such as the famous Boonsung Wreck, are often still accessible depending on daily weather and sea conditions, offering an incredible “fish soup” experience for macro lovers.
Make the Most of the Season with King Andaman Scuba Diving
Timing is everything, but having the right team to guide you makes the experience unforgettable.
Whether you want to catch the crystal-clear waters of December on a day trip or chase the Whale Sharks of March and April on a multi-day liveaboard, King Andaman Scuba Diving has you covered. Aboard our spacious, diver-designed vessel, the M/V Maxwell, our expert instructors know exactly where to take you to maximize your sightings during every phase of the Khao Lak diving season.
Don’t miss the best diving of the year! Visit King Andaman Scuba Diving to check our liveaboard schedules and secure your spot today.
