There are couple of diving places kuching. Old Club reef, New Club Reef are both near the hotel at sealine, ottoman reef, zeytun reef (maybe my spelling is wrong for the names sorry :/) are alternatives also i did not go for diving there but I heard there is place for diving at Dukhan too. For the equipment rental you can be a member of the club (annual fee is around 1400 QAR) and rent equipment or you can go to the dive shops at the site I mentioned above.

Hope it will help

Good luck

"What doesn't kill me; makes me stronger..."