evidence: Although the faceless cusk's snake-like shape resembles that of an eel, the strange, deep-sea animal is a true fish. The animal is closely related to the similarly serpentine pearlfish. 4 of 15 Cookiecutter Shark The namesake of the cookiecutter shark from the crater-like holes the shark takes out of its much larger prey. The bite marks left by this small, rarely-encountered shark are typically the best way scientists have to study the species. However, the cookiecutter shark's main food source is squid, which it consumes whole. Cookiecutter sharks have been caught over 12,000 feet deep but are typically captured at night by shallow trawls, suggesting this shark species may rise up to the surface at night. 5 of 15 Pacific Blackdragon Dorling Kindersley / Getty Images The female pacific blackdragons' sleek black body allows the fish to hide in the darkness of the deep sea and makes the animal well-suited for its characteristic ambush-style of attack. Using a light organ that dangles from its chin, the eel-like fish lures in prey before mounting an attack. Male pacific blackdragons are not equipped with these special features, are much smaller than females, and even lack the ability to feed themselves.