My wife took me there for our 5th anniversary last year. We stayed at Sandals...nice, fun resort. The diving was typical "resort" diving and I avoided the pre-dive check by proving I had dove the Caymans 3 months earlier. Otherwise it would have wasted a day doing a pool checkout dive.
The resort took the boat to Anse Chastanet one day and the diving was great. Interesting structure (where else can you shore dive a sloping sand bay, deep wall, shallow flat and cave all in the same dive?). There was lots of life (big and small) and the reef was in good condition. If your going to St Lucia for diving, stay in Soufriere. There's a lot of great shore/boat diving. The water was a little chilly when we went, so I'd rec a tropical skin or 3mm.
We dove a bunch of sites near the the Sandals resort (including offshore from an Amerada Hess oil tank farm) in the Northwestern part of the island. The better sites were in the Southwestern part of the island (Bay of Pigs and Anse Chastanet). By the way, if you are staying at Sandals, pay for the 15 min helocopter ride to the resort, the hour long drive made 2 of the women in our van physically ill from the ride on the twisting roads.
Here's a list of dive sites from the sponsored web site:
Anse Chastanet: One of the most dramatic spots for diving is the stunning Anse Chastanet reef in the southwest of the island. The shallows, with depths to 25ft can be entered directly from the beach. The reefs falls away from 20-140 ft in a unique coral wall that continues from Anse Chastaner Bay around the headland of Grand Caille and in towards the harbor of Soufriere, providing some of the best diving in St Lucia.
Anse La Raye: Known as one of the finest wall and drift dives in St Lucia, Anse La Raye can be found below a shallow wall. Interesting formations at the slope which consists of huge bolders, stimulate the eye and imagination.
Coral Gardens: Located at the base of the Gros Piton, the Coral Gardens offer breathtaking scenery above and below the water, where five finger coral runds from a depth of 15-50ft.
Fairy Land: At the point of Anse Chastanet, a plateau named Fairy Land slopes gently from 40-60ft. Since strong currents here keep the corals and sponges clean and the viewing is excellent and, this site is ideal for underwater photography.
The Key Hole Pinnacles: Voted one of the "10 Best Dive Sites" by Caribbean Travel & Life, The Pinnacles are described by the magazine as "four coral and gorgonian-encrusted seamounts that rise tantalizingly up from the ocean depths".
Lesleen M Shipwreck: The Lesleen M, a 165-foot freighter, was sunk by the Department of Fisheries in 1986 to provide an artificial reef. It lies upright in 60 ft of water near Anse Cochon on the west coast, just south of Marigot Bay. Divers can tour the ship in its entirety.
Superman’s Flight: Names for a scene on St Lucia for the movie Superman II, this site is a drift dive on a gentle wall that drops to 1600ft. Good visibility created by strong currents permits crystal clear viewing for underwater exploration. Divers can enter the water here at the base of Petit Piton.
Here's the web address:
http://www.stlucia.org/tour/map.asp
