You will not find many sites with much nice coral off any of the Hawaiian Islands ala the Caribbean. Mostly only small patches of relatively colorless stuff. Also, sparse sponge or vegetation for the most part. Look for relatively cool water temps, like 77 plus/minus 2 degrees, and modest viz, like 40-80'. Marine life is another matter altogether. Varieties of butteryflyfish, triggerfish, surgeon/doctorfish, etc. far out number those found in the Caribbean. Also, lots of turtles.
The Big Island has a wide variety of topography & excellent diving of the Kona coast. It is my first choice. Neat manta ray night dive -- the one at the now closed Kona Surf used to be almost guaranteed, but longer so. Action now is a bit north to Eel Garden Cove. Some excellent shops, including Dive Makai, Sandwich Isle Divers, Aloha Divers & Jack's Diving Locker, although these draw experienced divers. The less advanced might want to check out Eco-Adventures.
Don't miss Volcanoes National Park, rain forest outside of Hilo, or the coffee plantations. Roy's on Big Island, too. Have drinks at the Mauna Lani, near the Ritz-Carlton. Kevin Costner stayed in one of the 4,000 sq.' villas with a Mercedes sedan and valet while filming "Waterworld" -- you'll know why it ran so much over budget. Eat at Cafe Pesto, Donatoni's and La Bourgoyne.
For diving in general & shore diving/snorkeling in particular, check out web sites of Big Island Divers, Kona Coast Divers (but don't dive with this op) and Dick The Diver. Also do Phosphorescent Bay at night. Sharon's Place, Long Lava Tube, Hammerhead Point & Golden Arches also good. Can do shark cage dive with Hawaiian Divers. My favorite shore dive & an easy one is Place of Refuge you will nice coral here. If diving with EcoAdventures, be sure to do the "Toilet Bowl" -- really fun.
BTW, I very highly recommended that you purchase "Hawaii The Big Island Revealed": by Andrew Doughty & Harriett Friedman. Oustanding. If you need Hawaii marine life ID books, you can e-mail me.
Best regards.
DocVikingo
