Just returned from a fantastic trip to Belize.  Stayed at a great resort called Hamanasi.  Beautiful place, great staff, great food and plenty to do.  The property is small- about 20 rooms; you have plenty of space to be alone if you want or it's easy to get to know other people at the resort.

While I was there I was PADI certified for open water scuba diving.  The process was much easier than I thought it would be.  Belize was a good choice for that training - the water is warm and there is a lot of great underwater life to see.