About 235 miles (378 kilometers) east of Halifax, the ocean floor drops away. Nicknamed The Gully, this place is more like a drowned Grand Canyon, measuring a dozen miles (19 kilometers) across and, in places, a mile (1.6 kilometers) straight down to the bottom. These deep waters are home to the immense—and immensely curious—bottlenose whales, whom scientists believe to be the deepest divers of all ocean mammals.

(Text adapted from and photograph shot on assignment for "A Journey Down Old U.S. 1," December 1984, National Geographic magazine)