Monk seals get their name from their colour - their dark brown coat looks a bit like the robe of a monk - and from the way they live mostly alone, not in big crowds the way other seals do. A monk seal can grow up to 2.4 metres long and weigh as much as 300 kilograms. That's about the weight of four adult humans put together.
They love quiet sea caves. A mother seal will choose a hidden cave with a tiny opening, sometimes only just above sea level, and that is where she gives birth to her pup. The pup stays in the cave for weeks, learning to swim in the safe water inside before facing the open sea.
Greek conservationists work hard to protect them. Some islands have set up special protected areas where boats can't go close, so the seals are not disturbed. School children in Greek coastal towns often learn how to spot a seal cave and what to do (which is mostly: stay quiet, stay far away, and tell an adult).
If you are very lucky on a Greek beach, you might see one bobbing in the water with just its round head above the surface, watching you back. They are curious creatures - and they have whiskery faces a bit like a kind, sleepy dog.