In Greek mythology, Charybdis is a sea monster personifying dangerous beliefs in the Strait of Messina off Sicily. She was the daughter of Poseidon (god of the seas) and Gaia (goddess of the earth).
Charybdis, along with another sea monster, Skylla, is described in detail in the myth of Odysseus: "... in the interior of a high rocky mountain, high above the sea, is a great cave, around and within is a thick mist, there dwells Skylla. And even the gods tremble in terror before her. She barks and whines and howls, more terrible than a mammal. It has six pairs of legs, six long necks, a large head at the end of each, an open mouth with three rows of large teeth. When it swims past a boat, it can grab six swimmers at once with those mouths. In a lower rock not far from Skylla lives Charybdis, an underwater monster which three times a day swallows vast quantities of water, drinks up nearly half the sea until the bottom of the sea is visible, and three times a day spews the water out again. If a ship is near, it disappears into the bottomless throat."
Aeneas describes it thus: "When you come to Sicily, keep always to the left. You must avoid the sea monsters Skylle and Charybdis. Skylla resides on the right shore, hidden in a cave. She resembles a beautiful girl down to her hips and lures the ships to the rock with her charming face. The lower part resembles a monstrous fish. It is covered with blue barking dogs. On the left shore is the predatory Charybdis, which three times a day swallows the immense torrents of water and then throws them up again, the foam splashing up to the clouds."
Only two ships have escaped the Skylla and the Charybdis. The first was an Argonaut ship, but it was helped by many heroes and gods. The second was the ship with Ulysses aboard. It lost six crew members, but made it through.