The coelacanth is considered to be a living fossil. This class of fish was first seen in fossil records 350 – 400 million years ago. Some scientists believe that this is a likely ancestor of ours and speculate that this is the ancestor of the first vertebrates to walk on land.
This fish was only known to exist by fossil records but in 1938 a living version of this fish was found around the Comoros islands. These fish usually live in underwater caves ~300-700 feet (~90-215 meters) deep.
Find out more about the coelacanth at the Wikipedia: Coelacanth