What is the water like (warm/cold) in January?
Which beaches have showers to rinse off?

If you're staying on the island, Magan's Bay, Coki Beach, and Sapphire beach have showers to wash off with. If you want a truly magnficent beach, take the ferry to St. Johns and go to Trunk Bay. We just returned back from the Sun Princess and went to Sapphire Beach instead of Trunk Bay when we were in St. Thomas. It was very windy that day, so I thought the ride over to St. John would be a little rough for my hubby. It was very choppy in Sapphire Beach, so the snorkeling wasn't that good. Plus the beach was nice, but nothing like Trunk Bay. The water should be in the lower 80s. Have a wonderful cruise!