For those willing to don an air tank and wet suit, the marine world is one of the last places where it's possible to appreciate wild nature. The coasts of the U.S. mainland have an abundance of diving destinations, while Caribbean territories and the U.S. islands of the South Pacific offer a full menu of diving spots that will excite even the most experienced divers. Want to enjoy some world-class diving without digging out your passport? These destinations are worth the trip. (Text: Josh Lew)