We went last July and stayed at Accra Beach (in the South).
There is some snorkeling. We went to Carlisle Bay and saw some wrecks right off the beach. We also snorkeled between Speightstown and Holetown and saw sea turtles (as well as some nice tropical fish). Mullins Beach is nice for snorkeling too.
If you want, they have tons of vendors selling "sailing/snorkeling trips" (we went "on our own" with our 5 yr old son).
If you drive, beware, that the road signs are terrible (and there are lots of traffic circles). Stay away from Bridgetown if you don't want to get lost (the roads don't connect--they turn into one-way streets in the middle of town). After awhile, we just went around Bridgetown whenever we wanted to get anywhere.
Stuff to do--the Barbados Wildlife Preserve is really nice (you get to wander around with green monkeys and tortoises), Flower Forest is nice too-interesting plants, and the Graeme Hall Nature Sanctuary is a very pretty garden-type area (with lots of birds). The Barbados Museum to small but interesting (history of Barbados). The "Folkstone Marine park" is kinda lame (really just a place to snorkle), and the Flower Forest is not really worth the long drive. We wanted to go to Harrison's Cave, but it was closed.
One more thing.. The food is really expensive (like most places in the Carribean, I guess). "Roti"s are great!
Hope this helps. Have fun.