I am not aware of any snorkeling 'tours' unless you use one of the many charters for a day sail. There are numerous choices out of Red Hook so you need to decide if you want a smaller (up to 6 quests) or larger (30+) boat, degree of amenities, etc. Make sure you choose one with at least 2 stops, otherwise it is just a party boat. Not necessarily bad, but not what you are looking for either.
We used Wayward Sailor out of Cruz Bay. Very good, but not as convenient for you since it would require an early ferry from STT to STJ. We stayed on STJ so for us, Red Hook charters were not considered for similar reasons.

Whichever cruise outfit you choose, try not to miss a day trip to the Baths on Virgin Gorda, they are one of the best snorkels you'll ever do!

Make time to go over to STJ and check with LOW KEY watersports. My wife and I used them and they have everything you need to snorkel, plus they can tell you right where to go. There are a dozen places just around ST. J.
For a tour of St J, just as you get off the ferry ask for "Smitty" one of the local taxi drivers. We took a tour with him and he spent the time to get out and tell us about the island and about the history. Even pointed out treasure island, that I'am sure you read about in your younger days. His taxi has flames all over it like you would paint on a hot rod. Well worth the time and money spent to spend time with him.

From St. Thomas there are many, many different excursions that offer snorkeling. Everything from the super unique (www.bobusvi.com), to the all-inclusive, full day sail (www.newhorizonsvi.com), to the all-inclusive half-day sail ( http://www.treasureislecruises.com/Day_Trips/Ship_Wreck_Snorkel/ship_wreck_snorkel.html - this one has changed locales from Buck Island to Great St. James Island), to the full day powerboat excursions that visit the Baths on Virgin Gorda (www.newhorizonsvi.com and http://limnoscharters.com/)...the list goes on and on. Given that your experience is limited, I would recommend the Limnos trip to the BVI. Just remember to bring your passports or birth certificate w/ photo I.D. You will see and do lots on that trip, and if you are uncomfortable in the water they will help to familiarize you and make you feel at home. Pus all of the food and drink is included, they have shade or sun, fresh water showers...the Limnos is probably what you are looking for

I recommend two different trips:

Day Sail with the Nightwind. http://www.beachtops.com/nightwind.html Food, drinks, and gear included. If you rent a car from Budget you get a coupon. We have sailed with Steve 3 times.

New Horizons II motor boat trips to the BVI. You will need a passport. This trip is more expensive but new horizons offers the best rates and gets out to the Baths first because the boat is fast. Some snacks & all drinks are included. They will take you to some great islands. The Jose Curveo island is a great lunch spot. Plan on $20 per person for lunch and $20 entrance to BVI government fee. The "rodi" wrap is great. Chicken and potatoe curry. Also Budget rent a car has a coupon for this trip.

Essentially if you rent from Budget I believe you save about $200 on these two trips. Budget is located at the STT airport.

Email me if you have questions.

Amy,

If you had to guess, how long does it take to get from Cruz Bay to the Baths on New Horizons II?

Thanks

NH II takes about 1/2 an hour to reach the Baths from Sapphire Marina on STT. Check it out at http://newhorizonscharters.com/