A very deep channel in the Atlantic Ocean, somewhat shaped like a tongue, running along the eastern edge of Andros Island in the Bahamas.

Much of the Bahamian islands are surrounded by shallows of the Great Bahama Bank, around 10 feet deep. The Tongue cuts into this bank at a depth of 6500 feet.

The U.S. Naval Undersea Warfare Center does lots of testing here, because the surrounding shallows limit boat traffic.

A cool space shuttle image of the Tongue: