I have been going out on the Andaman Sea for over 20 years. It has never become ordinary. That is not something I say as a marketing line — it is simply true, and I have been trying to understand why for most of that time.
Here is my best attempt at explaining what makes this particular body of water so extraordinary, from a layperson who has spent more time on it than most.
The Andaman Sea sits between the Thai-Malay Peninsula to the east and the Andaman and Nicobar Islands to the west, forming a semi-enclosed body of water that is part of the northeastern Indian Ocean. Its defining visual characteristic — the reason it looks different to almost any other sea — is the limestone karst geology that runs along its eastern shore.
These karst formations are ancient coral reefs, deposited over millions of years, subsequently lifted by tectonic activity, and then sculpted by millennia of rainfall and wave action into the towers, islands, and sea caves that now characterise Phang Nga Bay and the coast of Krabi. Ko Tapu — James Bond Island — is a remnant karst tower. The islands of Phi Phi are karst. The hongs, the sea caves, the overhanging cliffs — all of it is the same ancient reef material, shaped by time into something that looks like a landscape invented by someone with a very good imagination.
What this means practically: the underwater topography is as dramatic as the surface. The rock walls drop vertically into the sea. Coral grows on the submerged karst faces in the same way trees grow on the cliff faces above. Swimming around the base of a karst island is like swimming around the base of a mountain — the scale is different to anything a horizontal reef can offer.
The Andaman Sea is genuinely that colour. Not filtered, not enhanced. The combination of white sand, shallow depth over the sand, and the clarity produced by the protected marine park areas around Phi Phi results in the specific turquoise-to-deep-green gradient that photographs so extremely well and that still, after 20 years, makes me stop and look when I see it.
The water clarity in the dry season — November to April — is exceptional. Visibility of 15 to 20 metres is not unusual at the better snorkelling spots around Phi Phi. You can see the bottom in 10 metres of water with the same clarity you see across a room. The reason is the combination of protected marine park status (no industrial activity, no trawling) and the dry-season reduction in terrestrial runoff that otherwise clouds coastal water.
Protected marine park status around the Phi Phi Islands and the Similan Islands has produced a marine environment that is measurably richer than equivalent areas without protection. Fish populations are larger. Coral coverage is more extensive. Species that require undisturbed habitat — turtles, reef sharks, eagle rays — are present in numbers that surprise first-time snorkellers.
The Andaman Sea is also one of the few places where whale sharks are encountered with regularity in the broader region — primarily around Richelieu Rock near the Similan Islands, which is one of the highest-rated dive sites on earth. The nutrient upwellings that attract whale sharks to this area are a product of the sea’s particular oceanographic conditions — the seasonal monsoon system that drives water circulation throughout the region.
The Andaman Sea is governed by one of the most reliable seasonal systems in the world’s oceans. The northeast monsoon (November to April) brings dry weather and calm seas to the eastern shore — Phuket, Krabi, the Phi Phi Islands. The southwest monsoon (May to October) brings rain and rougher conditions to the western coast of Thailand, while simultaneously producing calm conditions on the eastern side of the Malay Peninsula.
For the boat trips we run from Phuket, this means a reliable operating window that is one of the most predictable in tropical Southeast Asia. The November-to-April window is not just good weather — it is the ocean being in a particular phase of a global atmospheric cycle that has been operating for longer than human history.
I do not have a completely satisfying answer to this, which is perhaps the most honest thing I can say about it. Part of it is the scale — being at sea, with no land visible, in water that is genuinely clear, is an experience that the brain does not fully adapt to regardless of repetition. Part of it is the life — there is always something in the water that was not there yesterday, or a light on the cliffs at a particular angle that I have not seen before. Part of it is the stillness that is available on the water in the early morning, before the tour boats come out, when the sea and the karst islands and the sky are all there is.
It is the best office I have ever had. I recommend it.
— Captain Mark
Exceptional, uncrowded island day trips from Phuket. Family-owned and operated since 2004.
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