To the south of Phuket lie the twin islands of Koh Racha Yai (big) and Koh Racha Noi (small) which offer significantly better diving than do Phuket's western beaches. Almost all diving operators offer one day trips to both of the islands (although not on the same day) and some offer a two day live-aboard trip every week.
Racha Noi is popular for the more experienced diver, as depths are generally greater and the currents frequently stronger than at its sister island to the north.
The northern tip features a large pinnacle where spotting larger marine life is distinctly possible, while the southern point is a nice drift dive with the added bonus of having a beautiful little beach to visit during your surface interval.
We also have a wooden ship wreck at about 27 meters on the southwest coast of the island which although does not compare to some of the larger wreck dives in Pattaya, is an enjoyable deep dive. Not much grows on the wreck yet, but it attracts large amounts of reef fish. The diving here is definitely more challenging than Racha Yai, but the rewards can be much greater.
Muslim farmers and a few fishermen have lived on Racha Yai for years now, harvesting coconuts and fishing the waters surrounding the islands.