We took the same cruise in February 2009 and dove in Dominica and St Kitts, and had a great time.
In Dominica, we used Nature Island Dive in Soufriere and dove at "The Abyss" which is a wall that drops to 1500 ft just a yards off shore (the boat ride took about 15 seconds

). The second site, "The Pinnacle" I believe is its name was just as fun and impressive, a garden of corals and plenty of marine life, and it is only 2 to 3 minutes from shore

The pick up was in Roseau, and the drive to Soufriere takes 20-30 minutes, and much of the drive was mountainous so you should take that into consideration. We got back to the ship about 3:00 PM.
In St Kitts we dove with Pro Island divers and Auston (the owner & divemaster) picked us up with his diveboat docked near the Victory, and that of course was very convenient. We dove at a wreck, "The River Taw", which was cool and we had several beginners (ie not yet certified, including a junior diver boy age 12) dove it with no problems. The next site was "The Coconut Tree Rock", which is a large coral reef with a wall. Again the marine life and the corals were abundant, healthy and colorful. We got back to the ship about 1:00 PM.
The viz in Dominica was about 80 ft, and at St Kitts was about 50 ft for us.
I wish I could have dived in St Lucia, but the dive shops I contacted never reply, and I didn't want to use the ship dive packages, oh well :blinking:
Have fun on your cruise, take plenty of photos, and dive safely
Richard