We are looking for a reliably warm and sunny location in the Caribbean between Christmas and New Years. Water sports would be great; nightlife is not that important. Tranquility would be a plus.

what about Trinidad and Tobago? Two of the cheaper islands in the Caribbean, the former with (regionally speaking) relatively little tourist development but some fabulous and quiet beaches with a few hotels, Blanchisseuse and Grande Riviere being the best. Tobago is more conventionally Caribbean, with a large-ish resort area in its west, but a couple of gorgeous and quiet beach resorts elswehere, Castara and Charlotteville. Check the RG to T&T for the lowdown on both islands.

forgot to say: Tobago is better for watersports, with clearer waters, Great snorkelling (many manta rays near Speyside and healthy reefs nearby), and there's also the usual waterskiing, scuba, hobie cat boats too.