Dean's Blue Hole.

Plunging to a depth of 663 feet, Dean’s Blue Hole is one of the deepest underwater sinkholes on the planet. Located on the coast of Long Island, this sapphire-colored void creates a stark visual contrast against the surrounding turquoise shallows and white sand. The site is framed by a natural limestone amphitheater that shields the water from wind and waves, creating an unnervingly still surface. This lack of current and immense depth has made it the global epicenter for competitive freediving, most notably hosting the annual Vertical Blue competition. While elite divers disappear into its dark depths, the rim offers plenty for more casual visitors; the shallow perimeter is a hub for snorkeling among sea turtles, rays, and tarpon. For the best view, hike the surrounding cliffs to see the dramatic transition where the bright Bahamian sand drops into the indigo abyss.