with Breeze Hawaii. While they are a lower cost, kind of cattle herd operation, the instructor/divemaster/guide we had was awesome. He was what made the day. Granted, we dove some incredible places, but Dan's ability to speak fluent Japanese, Hawaiian, and English, enabled myself and the six Japanese divers I was with to have a terrific day of diving.
Depending on conditions, try to get to Stars. A series of lava tubes with an incredible amount of fish life, awesome ability to see what's hiding in cracks, crannies, holes.
Black Rock - More lava formations. Drop over the ledge to 85', sandy bottom and visit the resident white-tip reef sharks. I got within 6' of a 6-7' female and great photos. Spend a few minutes there, go back up the ledge and drift dive while the boat follows. 30-40' depths, look in the holes for octopi hiding.
I did 3 tanks that morning, all on the west side of the island.
Another day, I rented three tanks and did some solo diving at Waimea Bay on the North Shore. Nothing deeper than 45', but say insane amounts of fish. I stayed mostly on the north end of the bay. Ran all three tanks under 300psi. Saw barracuda, huge sea turtles, family of 7 squid from 6" to 18", unicorn fish, parrot fish, trigger fish, spiney lobster......
Waimea is also a fantastic snorkeling place during the summer when the surf is down.
For the most incredible hamburgers, Jameson's by the Bay in Haleiwa, I believe, further north. Also next to a great bay to scuba & snorkel in.
If you do want to call Breeze Hawaii, PM me and I can get you in touch with Dan. He is incredible, a great tour guide on the drive too.