This is basically the Ancient Greek equivalent of being between a rock and a hard place. Charybdis was a large whirlpool, and Scylla was a many-headed monster who snatched sailors off of ships and ate them.
scylla and charybdis
The saying "between a rock and a hard place" originated from the Greek mythological episode of Scylla and Charybdis. It refers to being stuck between two equally difficult or dangerous situations with no clear way to escape.
in the part where Odyseus is sailing in between them
scylla
Scylla and Charybdis are both Greek monsters. They both killed travelers. Scylla ate travelers and Charybdis drowned them by making whirlpools.
Charybdis was a sea monster in Greek mythology that was in the form of a whirlpool. She was paired with Scylla, another sea-monster that sailors didn't want to encounter. "Between Scylla and Charybdis" means having to choose between two dangers, either of which brings harm.
David Hugo has written: 'Between Scylla and Charybdis'
He chooses Scylla over charybdis because if they go to charybdis they would all die, but if they go to Scylla only six would die because Scylla has six heads and six mouths to eat with.
Charybdis was a giant monster, that sucked in water, creating a whirlpool, and Scylla was another monster, whose cave was high on a cliff, that had a small amount of space for a ship to sail through without being killed by Charybdis, though this was just as deadly because Scylla would launch one of her heads down and snatch up sailors, eat them, then go for another.
In Greek mythology, Charybdis and Scylla are not friends; in fact, they are adversaries. They are two sea monsters who are often depicted as being in close proximity to each other, creating a dangerous passage for ships to navigate. Sailors had to choose between facing Charybdis' powerful whirlpool or Scylla's deadly rock formations.
Odysseus chooses to pass by Scylla because, Scylla will only kill 6 men, one for each head. Charybdis will sink the ship, killing everyone. Circe has also advised Odysseus to do choose Scylla. Further, Charybdis is a visible danger, and Odysseus uses Charybdis to encourage his men to pass by quickly. Finally, passing by Scylla and Charybdis is given as the only way for Odysseus to get home from where he is.
charybdis a swirling whirlpool