Belize advice

[Clifonef]

I've conned my family into going to Belize in December, but the constituents demand more than diving.  They can be sated with beaches and birds, so we've decided to go to the Placencia (south) end of the country.  Does anyone have experience with the dive sites or dive operators in this area.  We are all newbies and easily impressed.

What about low-key accommodations?  Six that look good in the guidebooks are:

Lydia's Guesthouse
Sea Spray Hotel
Tradewinds
Blue Crab
Ranguana Lodge
Singing Sands

Tanks everyone ;D