What is 40 Fathom Grotto?

Deep Descent

World-famous 40 Fathom Grotto is a naturally formed sinkhole located in the heart of north-central Florida’s thoroughbred racing country. It is the only place in the eastern United States where you can train, dive or play in depths of up to 200 feet or more and still:

It’s no wonder then that dive educators from around the world consider the Grotto to be the Ultimate Training Facility.

Grotto Geology

Geologically, the Grotto is what is known as an in-line sinkhole. Sinkholes form when the earth and rock above an underground river become weakened by the flow of water underneath. Eventually, this earth and rock collapses. Much of this material is carried away by the current; that which remains forms what is known as a debris cone, which the river now flows up and over.

Sinkhole Diagram

Sinkholes seldom have perfectly straight walls (the Grotto is no exception). The Grotto’s sides slope outward — often at a substantial angle — resulting in a diameter at the base which is several times greater than it is at the surface. Divers need to bear in mind that, even though they may appear to be in open water, ascents must be made cautiously — lest you clobber yourself on an overhanging ledge.