If you have enough time, check out the Phi Phi Islands, the most visited and most famous attraction in the area, which gained fame after the filming of The Beach on Phi Phi Ley.
The scenery is literally spectacular, and this is foreseeably the most popular of all the full day excursions.
For divers, many islands offer prime sites, such as Dok Mai, Racha, and Shark Point.
The preferred choice however is the remote but renowned Similans, a chain of 8 islands 90 kilometres NW of Phuket, which according to those in the know, has some of the best dives in the world.
Deep Sea Fishing can be arranged privately or jointly with fully equipped boats in pursuit of tuna, marlin, shark, sailfish and other big ones.
Yacht Charters can be arranged by the day, or for longer, with or without crew.
These cool things can be arranged through the friendly staff of Amari Coral Beach Phuket.