Scylla and Charybdis team up to make passing through the Straight of Messina impossible – to be a safe distance from one meant being too close to the other. They were one of Odysseus’ many challenges during his epic journey. Scylla is a six-headed monster storied to have become that way after poisoning by the jealous wife of Poseidon who captured sailors off their boats and ate them. Charybdis is best described as a whirlpool bringing ships to the bottom of the sea. She was the daughter of Poseidon and converted by Zeus.