The Cookie cutter shark, also known as the Isistius brasiliensis, is a small but dangerous predator that leaves deep, circular wounds on its prey. It was discovered by French naturalists in the early 19th century, but its true threat was not realized until the 1970s. They are about 22 inches in length, with a dark brown or grayish back and a light underside. They have a unique ability to produce blue light thanks to phosphorus. The shark's mouth is equipped with sharp teeth which it uses to scoop flesh from its prey, leaving pit-like wounds. They are known to attack larger predators and have even been known to damage submarines. The sensation of their swaying movement underwater lures prey in, and their attacks are extremely painful. They have been found to attack marine animals and even humans, causing serious damage.