The Crevice, Guam

The Crevice is a narrow vertical slot in Guam's south-west reef wall, barely wide enough for two divers side by side, that plunges from 18 m at its entrance to over 50 m at its sandy floor, its walls encrusted with orange and yellow cup corals that bloom densely in the absence of direct sunlight. The slot's geometry creates a permanent thermocline where cool bottom water meets warm surface water mid-column, and at this layer spotted eagle rays often glide in from the open ocean to hover in the temperature gradient. Exiting through the top of the crevice onto the open reef wall delivers divers into a current-swept environment where schooling fish and the occasional hammerhead shark become visible in the blue water column below.