See if you can "hitch a ride", for a modest fee, with an outgoing two-tank
SCUBA diving boat. If the boat has space, you can come along and snorkel around the boat during the dives. Usually these dive boats leave around 9:00 AM and return by 12:30 PM. It is not what exactly you're looking for, but it is not bad at all for the
price you will be paying. Some areas, where the dive boat will
anchor could be in shallow waters (15 ft or so), others could be doing "drift dives"; ask about the locations of the dives before signing up. (I dove with Low Key
Water sports, Cruz Bay - St. John USVI, for years. It is a very well established outfit that offers reasonable rates. I have known
Captain Bob, for decades.) Have fun! Mauritz