Simon Dannhauer/Shutterstock As I breast-stroked from the boat to the rocky exterior of Thunderball Grotto in the Bahamas’ Exuma Islands, I wondered if the James Bond-famous cave would live up to the hype. Above me, where moments before had been crystal clear skies were now ash-gray clouds, the result of a sudden breeze; I paddled along, thoughts of a cold Kalik beer and a warm, dry towel swimming in the back of my mind. From the outside,...