A blue hole is created when the ceiling to an ancient cave system collapses in the ocean―Dean’s is thought to be the world’s deepest. Fin your way off the powder-white beach and watch the sand go from 5 to more than 600 feet deep in just a few kicks.
On-site secret: I found I could circumnavigate the entire blue hole by swimming along the cliff base and sandy shoals. On a light-wind day, it’s easy to snorkel the protective reef near the mouth of the small bay.
Keep an eye out for: jacks, tarpon, turtles, the occasional dolphin or porpoise―almost anything can wander in. Small reef fish stay in the shallows. When to go: all year; 242-338-0011 or grottobaybahamas.com.