Blue Hole (Big Pine Key)
The Blue Hole is an attraction on the island of Big Pine Key in the Florida Keys. It is an abandoned rock quarry that was used for nearby road fills and Henry Flagler's Overseas Railroad. The water it contains is mostly fresh and is used by various wildlife in the area, such as birds, snakes, alligators, key deer and green iguanas. It is part of the National Key Deer Refuge.
Blue Hole (Red Sea)
However, the Blue Hole is notorious for the number of diving fatalities which have occurred in the past. One local Tech-Diver puts the number of deaths over 130-200, and thus claims that it is the most deadly dive site in the world.