Did the two-tank Night Dive with Kona Honu Divers and it was fantastic - very clean and safe boat, great dive masters, great diving. Saw over 30 Manta rays feeding on plankton. Was $180 US per person included all equipment and suit - even a $1 contribution to conservation efforts!
I recommend only 3 dive sites off Kona, but it spectacular:
1. Night dive with mantas. Every night you can see more than 6 mantas in one place ( I saw 25). For me it best night dive sites in the world!!!!
2. Harbor . In harbor lives 3 tiger sharks. One of them probably 5 meters and so fatt ( it biggest tiger shark what I see). During dive you can meet eagle Ray , gray reef shark, Dolphins , mantas, turtles and etc etc etc. I meet also monk seals.
3. Manta cleaning station.