Ocean sunfish, or molas, look like the invention of a mad scientist. Huge and flat, these silvery-gray fish have tiny mouths and big eyes that vanish into an even bigger body with a truncated tail. Topping out around 5,000 pounds, the mola is the world’s heaviest bony fish. (That category doesn’t count sharks and rays. The whale shark is another 10 times bigger.)
With their tank-like bodies, molas were clearly not built for life in the fast lane, but they hold their own against the faster and flashier fishes and are able to live in almost all of the world's oceans. They are know to spend time near the ocean surface but tagging shows that molas are also prolific divers and migrate long distances at depth.
They grow to a maximum of about 10 feet long and are often taller than they are long, up to 14 feet from dorsal fin tip to anal fin tip. They have a truncated tail fin referred to as a clavus—a scalloped fringe of muscle along their blunt rear end, which they use as a rudder.
clipped from: www.montereybayaquarium.org 
