St THomas--Coral World is the only reasonable choice IMHO. Check their web site--there are sometimes discount coupons there and/or in the tourist magazine that is handed out at the port. Very easy to do on your own. There is an aquarium, walk in underwater viewing area, touch tanks, snack bar, etc. You can swim at Coki beach(across parking lot). Taxis readily available. CW gives you a wrist band so you can come in and out from the beach to use restrooms, snack bar, etc. as desired. Beach is free with decent snorkeling. Family friendly (that's code for swimwear required).