I spent some time there back in '99 and contacted the local BSAC club on the island (South China Dive Club) they meet at the boat club in Aberdeen (south part of the island). They're a friendly lot and were very welcoming to me as a visitor, even loaning/renting some equipment. You can check out their website at
website Alternatively there's a club in Kowloon, but I don't know any details for them.
The diving there is similar to diving in this country, but warmer and of course different marine life etc. Viz can be good or bad, again similar to UK. WAter temperature when I was there (July/August) was 28-30 degrees, so I managed quite well with swimming trunks and a T-shirt. You may consider a wetsuit though as depths below 15m can reduce noticeably in temperature.
Rob
Facts about Aberdeen
It is in Hong Kong- Aberdeen is in the South China Sea.
- The typical depth is 0-10 Metres 0-30 Feet.
- The typical visibility is 0-3 Metres 0-10 Feet.