Hamanasi is really an amazing place. We went there...

Hamanasi is really an amazing place. We went there to get our PADI Open Water Diver certification. The dive staff were competent, friendly, and helpful. (And we got our certs!)
The rooms are awesome. We stayed in two rooms just due to availability. The beach front suite is wonderful and a bit smaller than the deluxe treehouse (really a multiroom suite). Both have emaculate furnishings and amenities.
The restaurant is wonderful and serves an early breakfast for divers (and everyone else too).
Keep in mind there's only internet access in the main building and it's not the fastest. There are some games in the main building and you may want to bring some of your own, too.
If you prefer beach front, get a suite. The Treehouse rooms are private and huge!
Anyway, definitely a great place and we hope to be back again some day.