I lived in Hawaii for 3 Years I dove in Kona quite a bit. There are GREAT night dive options in Kona. MANTAS GALORE!!! also ask the locals about turtle beach. you can head right in the water off the beach there and after getting past the breakwater there is some awsome caves to play in. My dive master is in Maui if you make it over there I can hook you up with a great bunch of divers. Good luck.
A.K.