I would rate the Westin's beach no better than "OK" (meaning better than anything we have here in Michigan, but not St. John's best by any stretch). By all means, check out the North Shore beaches like Hawksnest, Trunk, Cinnamon, etc. They're what St. John is famous for.

Elizabeth,

Due to the geographic orientation of Great Cruz Bay, and the fact a fair number of boats "harbor" there, I wouldn't describe the water as the "freshest". The "beach" was manufactured by the hotel and to me its a little Disney-like. That said it's probably better than most east coach beaches (outside of Florida) as many are fouled a bit by rivers. I would agree with Regan's suggestions but would suggest getting to Trunk before or after the cruise ship passengers. I would also add Maho, Gibney, and Jumbie on the North Shore, and I would also suggest a visit to Salt Pond on the South Shore. There are 39 beaches on St. John so I'm sure you will find something you will like. There is a great book that describes them in detail that you can pick up down there "St. John, Fins, Feet, and Four Wheel Drive" by Pam Gaffin. Have a great trip!

With all the beautiful beaches on St. John you will have plenty to choose from. The beach at the Westin is as described a man made beach in a boat harbor and we all know what they flush. If you have kids they will like the toys on the Westin Beach but that would represent the only reason to spend any significant amount of time on their beach.