Charybdis was a legendary sea monster who took the form of a malevolent whirlpool lurking in the Strait of Messina.
She was depicted as a ravenous, grotesque figure with flared nostrils and wildly flailing mouths through which she three times a day swallowed massive gulps of the sea's saltwater before violently belching it back out.
This created powerful maelstroms capable of sucking in and destroying even the largest ships foolish enough to pass too close.
The monstrous Charybdis lived directly across the strait from another hazard - the six-headed beast Scylla.
Avoiding them both required expert seamanship, for which Odysseus famously threaded the middle course in his legendary journey home to Ithaca.
Charybdis embodied the unpredictable, destructive chaos of the untamed sea.

Excerpt from Homer's Odyssey

Book 12, lines 103-108
Homer:
”Beneath, divine Charybdis sucks black water down.
Three times a day she spurts it up; three times a day she glugs it down.
Avoid that place when she is swallowing the water.
No one could save you from death then, even great Poseidon.”

Book 12, lines 135- 246
Homer:
“On one side, Scylla; on the other, shining Charybdis with a dreadful gurgling noise sucked down the water.
When she spewed it out, she seethed, all churning like a boiling cauldron on a huge fire.
A froth flew high, to splatter the topmost rocks on either side.
But when she swallowed back the sea, she seemed all stirred from inside, and the rock around was roaring dreadfully, and the dark-blue sand below was visible.
The men were seized by fear.
But while our frightened gaze was on Charybdis, Scylla snatched six men from the ship- my strongest and best fighters.”