Only got 4 dives there, and 2 were training dives, so take with a grain of salt. My impression was diving over flat bottom around 40 feet deep, give or take, maybe 50 foot viz., warm water, decent reef, some typical Caribbean sea life. Well worth diving when I was there; not a place I've been driven to purposefully seek out.
I don't think you'll find many week long dive reports for St. Thomas here, which seems to get a decent amount to dive traffic in relation to being a high volume cruise ship stop.
None of which means it's bad. It's known as a big Caribbean shopping destination, I believe it's said to have good beaches, and you can take a ferry to St. Johns (known for beautiful beaches and snorkeling) and St. Croix (which seems to have a better rep. for diving?). Being a big cruise port, you've got a lot of entertainment excursion options.
The dive op. I used in St. Thomas as Admiralty Dive Center, and we were very pleased with them.
Bear in mind cruise divers (which I was) are new to the dive op. each day, and might be unlikely to be taken to more demanding or more delicate sites, since the staff don't know what kind of divers they're dealing with.
@Corrinado posted this: