The boom is louder than a lightning strike. A column of water rises taller than the towers of Troy, spume and spray crashing across the strait, and as the mist clears you see what lies beneath: a vortex moving against every other current, a mouth of water grinding and roaring. She breathes on a clock. Forty breaths between eruptions, regular as day and night. There is no choice but to row across her face and pray she is exhaling when you pass. The strait is two evils on two cliffs and Charybdis is the one that can kill the whole ship at once. Circe’s instruction is to keep close to Scylla’s wall and pay her toll, because Charybdis pays in everyone. [SPOILER: After Zeus shatters the ship for Helios’s cattle, Odysseus rides the wreckage straight back into her current. He has nothing left and no men. He hauls himself up into a fig tree growing from the cliff face and hangs there with his palms splintering on the bark while she swallows the keel and the mast and pulls them down out of sight. He counts. He waits. She vomits the timbers back up and he drops onto them and rides them out. Even monsters give back what they cannot keep down.]
Charybdis
A whirlpool that breathes. Every forty breaths a column of sea explodes upward, then the water sucks down hard enough to swallow timbers whole.