Some photos of what you can expect to experience under the surface while in St. Thomas can be found under my profile; Will be there over New Years myself. Do most of my diving of a private boat however, have made a couple of dives with Red Hook Dive Center (as reliable as any), usually a morning and an afternoon trip with a once a week night dive.
Coke Dive Center is another (right at Coke Beach). Terriific place for shore drives, nice reef right off shore; more than nice at night.
With either, do suggest you make reservations in advance as trips often fill quickly.