In Greek mythology, the sea monster that creates a massive whirlpool by swallowing and expelling water is Charybdis.
Charybdis appears in Homer’s Odyssey as a deadly maritime hazard opposite Scylla in the Strait of Messina. Three times a day, she swallows a huge quantity of seawater and later belches it back out, producing a whirlpool capable of dragging ships beneath the surface. Odysseus is forced to choose the lesser danger and sails nearer Scylla, losing six men.
Some ancient and later accounts treat Charybdis as a monster beneath a rock; others make her essentially the whirlpool itself. A mythological genealogy identifies her as a daughter of Poseidon and Gaia. In another story, Zeus punished her for helping Poseidon flood lands and transformed her into a perpetual sea hazard.
Charybdis is often mixed up with Scylla, but their roles differ: Charybdis threatens an entire vessel through engulfing water, while Scylla attacks individual sailors. The expression “between Scylla and Charybdis” means being trapped between two comparably dangerous choices. Real currents and whirlpools in the Strait of Messina may have helped inspire the legend.