A grown-up monk seal can be 2.5 metres long - taller than most adults - and weighs up to 300 kilograms. They have short brown or grey fur, a round head and big dark eyes. People think they got the name 'monk' because their head looks a bit like the hood of a monk's robe.
Monk seals don't go out on the beach like other seals. They are very wary of people, so they raise their pups in sea caves. The pup is born on a hidden beach inside the cave, and the only way to reach it is to swim underwater through the entrance.
They eat fish, octopus and squid. They are amazing swimmers - they can dive 100 metres down and hold their breath for up to 15 minutes. Their whiskers help them sense fish moving in the dark water.
Mediterranean monk seals were once so common in the sea that ancient Greek and Roman coins had pictures of them on. Now they are so rare that scientists in Turkey work hard to keep their caves secret and quiet, so the pups have a safe place to grow up.