The Jalousie in St. Lucia will meet your requirements perfectly. You can shore dive from the beach or take boat trips. I was diving there in February and was very impressed, and I've dived in quite a few top dive areas.

I didn't stay at The Jalousie so I can't comment on the property. I was at LeSport www.thebodyholiday.com

There are also lots of rainforest walks and many other activities.