She was a sea-monster,whose gigantic whirlpool swirled in the Straits of Messina opposite the cliffs of the monster Scylla.
Charybdis aided her father Poseidon in his feud with Zeus and, as such, helped him engulf lands and islands in water. Zeus, angry over the land she stole from him, captured and chained her to the sea-bed. Charybdis was then cursed by the god and transformed into a hideous bladder of a monster, with flippers for arms and legs, and an uncontrollable thirst for the sea. As such, she drank the water from the sea thrice a day to quench it, which created whirlpools.
Odysseus faced both Charybdis and Scylla while rowing through a narrow channel. He ordered his men to avoid Charybdis, thus forcing them to pass near Scylla, which resulted in the deaths of six of his men. Later, stranded on a raft, Odysseus was swept back through the strait and passed near Charybdis. His raft was sucked into her maw, but he survived by clinging to a fig tree growing on a rock over her lair. On the next outflow of water, when his raft was expelled, Odysseus recovered it and paddled away safely.
The Argonauts were able to avoid both dangers because Hera ordered the Nereid Thetis, Achilles’ mother, to guide them through the perilous passage.