Hi Champ, welcome to Cruise-chat. We did a great snorkel in Grand Turk last December, we booked it through the ship. They stopped at 2 areas 1 for the coral and 1 for the fish. The water was crystal clear, the coral was beautiful and the fish were plentiful. Half Moon Cay is a private island, great beach day. By all means do a swim with the dolphins, it is the most awesome experience I've had. We did ours in Cozumel at Chankanaab Park. The dolphins are amazing creatures, they are so powerful, yet so gentle to humans. They really seem to enjoy interacting with you. We bought the video they took, and a couple of pictures. Be sure you do a swim and not an encounter. The swim allows you to be in the water with them. It's worth every cent. Atlantis is a fun way to spend time in Nassau as well, there is a public beach right next to it. Best wishes and have a wonderful time. I'll warn you now, cruising is addictive