Oahu Scuba Diving Locations
Kahuna Canyon (Mokoleia)
Rainbow Reef (Ala Moana Park)
Hanauma Bay (diving conditions are usually calm year round)
Fantasy Reef (boat access only)
Big Eel Reef (boat access only)
Turtle Canyo (boat access only)
Kahala Barge (boat access only)
Hundred Foot Hole (boat access only)
The Mahi (186 foot Navy Minlayer, 90 feet off of west side, between 60 and 78 feet deep; 4th best shipwreck in U.S.)
Gull Wing Corsair fighter plane

Oahu has a great bus system! Depending on where you plan to go, you might not even need to rent a car.

Franko's Fish Cards depicts some Oahu Scuba Diving locations and includes images of over 80 species of Hawaiian fish.