Frilled Shark

Humans rarely encounter frilled sharks, which prefer to remain in the oceans' depths, up to 5,000 feet (1,500 meters) below the surface. Considered living fossils, frilled sharks bear many physical characteristics of ancestors who swam the seas in the time of the dinosaurs. This 5.3-foot (1.6-meter) specimen was found in shallow water in Japan in 2007 and transferred to a marine park. It died hours after being caught.

Giant Spider Crab

Thought to be the largest arthropods on Earth, giant spider crabs spend their time foraging on the ocean floor up to a thousand feet (300 meters) deep. These rare, leggy behemoths, native to the waters off Japan, can measure up to 12 feet (3.7 meters) from claw tip to claw tip. This five-foot (1.5-meter) specimen was photographed in Japan's Sagami Bay.

Atlantic Wolffish Pair

The sinister-looking Atlantic wolffish makes its home in the rocky coastal depths up to 1,600 feet (500 meters) below. Reaching 5 feet (1.5 meters) long, wolffish have conspicuous dentition suited to a diet of hard-shelled mollusks, crabs, and sea urchins. This mated pair was found in a deep-sea den off the coast of Maine.

Fangtooth Fish

The nightmarish fangtooth is among the deepest-living fish ever discovered. The fish's normal habitat ranges as high as about 6,500 feet (2,000 meters), but it has been found swimming at icy, crushing depths near 16,500 feet (5,000 meters). Fangtooth fish reach only about six inches (16 centimeters) long, but their namesake teeth are the largest, proportionate to body size, of any fish.