Charybdis

Kharybdis or Charybdis (IPA: /kəˈrɪbdɨs/; in Greek, Χάρυβδις) was a sea monster, once a beautiful naiad and the daughter of Poseidon and Gaia. She takes form as a huge bladder of a creature whose face was all mouth and whose arms and legs were flippers and swallows huge amounts of water three times a day before belching them back out again, creating whirlpools. Charybdis was very loyal to her father in his endless feud with Zeus; it was she who rode the hungry tides after Poseidon had stirred up a storm, and led them onto the beaches, gobbling up whole villages, submerging fields, drowning forests, claiming them for the sea. She won so much land for her father's kingdom that Zeus became enraged and changed her into a monster.

The myth has Charybdis lying on one side of a blue, narrow channel of water. On the other side of the strait was Scylla, another sea-monster. The two sides of the strait are within an arrow's range of each other, so close that sailors attempting to avoid Charybdis will pass too close to Scylla and vice versa. The phrase "between Scylla and Charybdis" has come to mean being in a state where one is between two dangers and moving away from one will cause you to be in danger of the other. "Between Scylla and Charybdis" is the origin of the phrase "between the rock and the whirlpool" (the rock upon which Scylla dwelt and the whirlpool of Charybdis) and may also be the genesis of the phrase "between a rock and a hard place