This animal isn't very well known, but it's quite creepy. It's called the cigar leaf shark or cookie cutter shark.
This is a very small shark that lives in all the warm oceans of the world, measuring less than 50 cm in size, but it will attack anything. They have even damaged submarines.
They live at depths of up to 4,000 meters, but come up to the surface at night to feed. Their hunting strategy involves taking a bite in one go, tearing off a part of their prey, and then returning to the deep sea.
They are called "cookie cutters" because they leave distinctive scars on their prey.
While attacks by these sharks are rare due to the depths they inhabit, there has been at least one reported incident: an attack on a man swimming in the open sea at night. However, swimming in the open sea at night is generally not a good idea…