Levi, if you still have Hawaii as a possibility I can add the following:
The water sems to get warmer and the coral growth more significant as you head from northwest (Kauai) to southeast (Hawaii). Although the SE islands are newer in age, I found the most spectacular coral colonies and life along the lower half of the Kona Coast (from the Waikoloa area parks about 20 mi north of the airport down to Cooks Monument area). We took a snorkeling cruise down to the Cooks area (Kealakekua Bay) and that was really cool.
Maui was OK, and there is a very nice park at the NW end of the island by Kapalua. Otherwise it was neat, but nothing to blow off your socks.
Oahu is really, really developed and if you're looking for a nice natural setting you're better off on one of the other islands. Hanauma bay used to be a nice, protected snorkeling bay with tons of fish and plenty of rocky areas (no coral) many years ago. However, as of 15 years ago or so it has become over-run and as someone else mentioned, it smells like a big hot tub of sunscreen.
Kauai is really nice, especially on the far north coast as you proceed counterclockwise around the island. There are some amazing tidal flats beneath the Princeville hotel where I've done some great collecting, and Hanalei Bay is stunning ... nice wide beach with mountains in the background. If you continue on the road past Hanalei to the end of the road, there's a couple nice reefs out there but nothing like Kona / Cooks.
Hope this is helpful ... on the collection reference, I've done collecting at multiple points on three islands (Hawaii, Maui, Kauai) and enjoyed them all with the Princeville Hotel flats being my favorite. However, to get the stunning visuals I would go first to the Kona Coast and possibly Molokini as I've heard that is neat.