There are 7 main islands in the Hawaiian chain. Nearly all of the SCUBA diving can be found on four islands; Hawaii (Big island), Maui, Oahu and Kauai.
The Big Island, Hawaii offers a spectacular night dive with the Manta rays. Try to avoid beach diving around Honokohau (it is pretty challenging). A good easy beach entry can be found at Place of Refuge.
Maui is famous for Molokini crater. The Hammerhead sharks love to hang around off of the sheer 400 foot underwater cliffs. Contrary to popular myth, there are a number of great shore dives around Maui such as Ahihi Cove and Makena Landing.
Oahu offers some of best wreck dives around. Wrecks like the Corsir and the YO-257. Most dive charter will pick you up right from your resort. For an easy beach dive look no farther than Shark’s Cove.
Kauai or the Garden Island offers some great beach dives. Tunnels Beach can be found on the North shore and it is worth the trip. Around the island there are two great lava reef structures. Take a dive charter to Ni’ihau or “Forbidden Island”. Here you will finds sharks and monk seals all around.