This is the "underwater" section, so I assume you mean underwater? I thought Honolua Bay on the NW side of the island was the best. It's a little murky at the shore, but once you get out into the water, it clears up and you'll definitely see sea turtles, tons of fish, etc. We followed an octopus around for about 10 minutes -- he was changing color and texture every time he settled onto a rock! That was just about the coolest thing I have ever witnessed from nature in person.
Have a look at
our gallery from Maui gallery from '05. If you see a shot and you want to know where it is, feel free to post here or PM me.
Oh, and lock your doors and don't leave any valuables. I don't mean to scare you... it's not a dangerous place, but we did see broken glass evidence of break-ins.