Bowmouth
Contributor
Water temps are in general between 28-30 Celsius. Some sites have frequent cold water upwellings and temps may drop to 26 Celsius. Most divers here use 3mm shorties but when diving on Live-aboards I recommend at least 3mm full-suit (I tend to freeze easily and use 5 mm full with 3mm hooded vest on top).
Currents can be strong but most sites have "high-profile" reefs that offer good shelter from current on at least one side of the reef. At some sites you may be able to drift with the current during your dive.
Visibility comes and goes; can be as poor as 5 meters (example: King Cruiser Wreck) and as good as 30++. Further away sites tend to have the better vis. Incoming tides usually bring better conditions than outgoing tides.
"House Reefs" in Phuket (Kata Beach) are ok and do offer some nice creatures but are not as good (colorful/diverse) as the day-trip and Live-aboard dive destinations.
Local diving in Krabi (need short longtail boat ride) is very nice and offers something for everyone (nice reefs, lots of fish, creatures,tunnels, caverns,short walls...)
