Nassau has a larger choice of hotels and is busier than say, Freeport, which is more laid back, and not quite as many hotel choices.
Most major airlines have nonstop flights from the northeast, possibly out of N.Y., and if you connect from Florida, you may not always be on a jet, probably a turboprop, but the flying time is not long--from FLL, about 25 minutes to Freeport by jet, add 10 minutes to Nassau. Twenty minutes more to each by turboprop.
Snorkeling is excellent most anywhere in the Bahamas, just find a beach, and dive in. There are diving and snorkeling operators who can take you out for a day or half day by boat.
Check out the Bahamas website for more info.
Hope this helps, have a great trip.
bj-21.