Waikiki on The Island of Oahu in Hawaii is a great place to go to do self directed scuba diving. Hawaii has so many different types of scuba diving and Waikiki has almost every type within 1 hour. You have wreck dives off Diamond Head, Shore Dives at Electric beach, Portlock with its large drop in. Lava tubes up at Sharks Cove, and tons of fish at Hanama Bay, including some pelages, and if you have your own scuba diving equipment it can be quite inexpensive. Even if you rent gear You can shore dive allot of different spots near Waikiki like Hanama Bay which basically is a giant aquarium filled with all sorts of beautiful fish. They have a tram that takes you down and back up. There is a lot of gear lugging to do this dive, but worth it, as it is one of the best dives in Hawaii. Electric Beach up at the power plant on the west side towards Makaha, has Giant turtles which can be found under the ledges hiding from the sharks, that you will most likely never see.