Ну, для тех, кому лениво потратить 5 минут в интернете на поиск информации:)
Diving Season
You can visit the Koh Samui and Koh Tao diving spots year round, but the very best conditions exist from March to September, which is when the resort areas on the Andaman coast have their low season. During these months you might experience visibility in excess of 30m.
Silhouette of a whale shark, diving at Sail Rock, Gulf of Thailand
Whale sharks, one of the drawcards of the area, are most frequently spotted in March and April and again in September and October. Other sharks are best seen in the Gulf of Thailand in times of cooler water temperature such as October and December when you might experience seas around 27°C, although that is only a few degrees lower than the annual high of about 30°C.
October to November brings the Northeast monsoon winds and surface swells to the islands, reducing visibility by about 30%. It's pretty rare that any daily dive trips are cancelled from here due to bad weather, but speedboat rides can be somewhat bouncy.
It can also be windy and wet in the Gulf from November to February so it may be better to go diving in Phuket, Phi Phi or the Similan Islands then.
http://www.divetheworldthailand.com/sam ... -sites.php
а что такого говорят? еще никто не жаловался.. 
