Dean’s Blue Hole is the second deepest Blue Hole in the world (twice as deep as any other blue holes in the Caribbean), and the second largest underwater chamber. It is 663 feet deep or 203 meters and approximately 80 x 120 feet round (25 x 35m) at the surface. The hole then forms a neck about 60 feet (20 m) then widens again on the way down to a diameter of 330 ft (100m). It is enclosed on 3 sides by rock cliffs and on the third side is a turquoise lagoon. A powder white beach runs the coastline of the lagoon.
The blue hole is always calm. There are never any waves inside Dean’s Blue Hole. Diving into the hole on a clear day is beyond words. It is like diving into a vast underwater cathedral. You will see a school of tarpon, friendly turtles and other tropical reef fish.

No one knows how the hole was formed. Most Blue Holes in the Caribbean are formed when limestone chambers caved in. Guesses state that perhaps two large limestone chambers were close together at the time of a caving.