Blue holes are roughly circular, steep-walled depressions, and so named for the dramatic contrast between the dark blue, deep waters of their depths and the lighter blue of the shallows around them. Their water circulation is … See more

Blue holes formed during past ice ages, when the sea level was 100–120 metres (330–390 ft) lower than at present. During these times, the … See more

Many different fossils have been discovered that indicate the type of life forms that existed in blue holes. Other life forms such as … See more

The chemistry of blue holes vary greatly depending on how they were formed. All blue holes have a layer of freshwater at the surface and more … See more

Blue holes are typically found on shallow carbonate platforms, exemplified by the Bahama Banks, as well as on and around the Yucatán Peninsula, such as at the Great Blue Hole at … See more

Sediment accumulation is unique in blue holes. Sedimentation occurs at the center of holes rather than the edges. Many different kinds of sediment help preserve fossils and climate … See more

Exploring blue holes requires a level of competence and equipment appropriate to the depth and overhead penetration. In 2009 a team of scientists set out to study seven of these blue holes in the Bahamas. Through over 150 dives, the scientists, led by Keith Tinker, … See more