Dean's Blue Hole

On the coast of Long Island in the southern Bahamas, a small crescent of white sand curls around a patch of sea that suddenly turns from pale turquoise to ink. That dark disc is Dean's Blue Hole, a vertical shaft in the limestone that drops to about 202 metres — the third-deepest blue hole known in the world. At the surface the opening is only some 30 metres across, but below the water the cavity widens into a chamber roughly 100 metres wide, so that a swimmer floating over the rim is hanging above a vast hidden room.

Blue holes form in carbonate platforms like the Bahamas, where the bedrock is soluble limestone. Geologists offer two explanations for this one: either corrosive water rising along a fault dissolved the rock from below, or the roof of an underground cavern collapsed and left a drowned pit. Either way, the result is a pit with near-vertical walls, set in a sheltered bay where the sea is usually calm and exceptionally clear. The contrast is the point of the place: a few strokes from the beach the shallow sandy bottom simply ends, and the colour falls away into darkness.

Low limestone cliffs frame part of the bay, with a lip of rock overhanging the water, and people jump into the hole from about nine metres up. Snorkellers can drift over the edge and watch the walls vanish beneath them, or explore the marine life along the beach. The same qualities — great depth in calm, protected water, reachable straight from shore — have made the site a world centre of freediving. The Vertical Blue competition is held here, and many depth records have been set in the shaft; in April 2010 the New Zealander William Trubridge reached 92 metres without fins, a record in the discipline at the time. The sport's risks are real, and the hole has also seen a fatal accident during a record attempt, in 2013.

Clarence Town, the island's small capital, lies just to the east. The setting remains unspoiled — an empty white beach, a protected cove, a few rocks and the circle of deep blue — and much of its power comes from how little else there is: no buildings frame the view, and the drama is entirely in the colour of the water.

Getting there

Dean's Blue Hole lies a few kilometres west of Clarence Town on Long Island, and about 12 km south of Deadman's Cay Airport (LGI), which has flights from Nassau, some 320 km away, and Stella Maris. The site is reached by road, and a brief walk from the parking area brings you to the beach. The nearest city on the map, Banes in Cuba, is across open sea and not a practical route.