Only dove in St. Lucia of the 3 ports.
In St. Lucia, we booked with Dive Fair Helen. They had a smaller fast boat to pick us up from the cruise port to take us to their shop (further south). After the paperwork and getting gears for those who needed, we headed south.
We had 6 in our group (myself as diver and 5 snorkelers). I had requested the site Superman's Flight by the petite piton and we did to there.
The cruise ship doesn't sail by the pitons, so if you want to see it, you'd need to go on a boat excursion. We were glad we were able to see them from sea. You can see the pitons much better from sea, than from inland.
The lunch served on the boat was quite good. After that we had arranged to be picked up near the pitons for a land tour of the island before getting back to ship. It's a long drive through windy road back. So allow at least 2 hrs for sightseeing and driving back.
At Superman's Flight it is drift dive by the wall. The second dive was also good. Did not see a lot of big fish, but lots of small ones and nice colorful corals.