I'm planning a sailing charter in the Caribbean around Christmas -
7-10 days with captain for two couples.

I've never been to the Caribbean and am looking for advice on which
island group would best fit our interests:

snorkeling and diving,
lack of crowds,
unihabited or islands still in their natural state,
close distance between islands.

We're not interested in nightlife or cities.

I'd love to hear any advice, ranging from where to go, favorite
charter companies, etc.

Thanks.