Some of the best Caribbean shore excursions available don't actually involve the shore at all, but rather the ocean surrounding it. That's certainly the case in Tortola, part of the British Virgin Islands, where both snorkel and SCUBA diving packages are available.
Certified divers who bring their Open Water certification card will be able to explore the remains of the RMS Rhone, one of the more famous shipwrecks in the Caribbean. This Royal Mail ship sunk during a hurricane in 1867 and has delighted divers ever since. It's even been featured in Hollywood productions, like the 1977 movie "The Deep."
Accompanied by your guide, you'll get the chance to explore the bow of the ship on the first dive, along with the colorful coral that now calls the boat home. Some divers have even been known to glimpse sea turtles here. The second dive explores the midship portion of the vessel and lets travelers spend more time underwater.
Not certified for diving? There are still snorkeling excursions available in the same general vicinity. Snorkelers will get the chance to view many of the same creatures and coral, and while they won't get to see a cool shipwreck, they will have access to a number of caves and rock formations.