Between Scylla and Charybdis

Scylla and Charybdis is 2 ancient greek monsters-that located so close to each other, to ships to HAVE to choose between them..both of them mean someone will die: Scylla-she look like 6 dogs headed hydra monster, of atleast 20meters in size, she have a humanoid like body on top of her, her human upper body-light bluish skin, long black hair, naked body, evil scary eyes, sharp teech, fish like ears, gills on neck and on body, from her stomach, there are six grotesque heads-each of them have long necks, dogs faces and mouthes, red eyesed-...she have 12 tenticles as legs. She living on big cave in mount-when ships getting to her, she SURELY, will ate 6 of humans..but if ship will be slow, she will be able to eat even 12 of sailors..if everyone will try to hide inside ship, she can easily break ship apart and them everyone will die..she cannot be killed...she represent fear of greeks about sharp falling stones from mountance.. Backstory: she have 2 versions of story:

1. She daughter of 2 sea monsters-monster sense birth..no drama..
2. Once she was a beautyful sea nymph, so beautyful even sea god Glauce fall in love with her...but she wasn't like him, so he go to witch Circe to ask her for love potion, didn't know that Circe herself loving him..so she give him a poison, not love potion..and when Scylla drinked it, she transformed into human fliesh eater monster.. Personallity: she cruel, maniac, sadistic, hungry, love eating, she ACTUALLY can talk and have a mind..but she still merciless monster... Powers: immortality, unnatural strengh, big size, cannot get hurt On the other side, there is a Charybdis: Extremly gigantic whilpool that openning her mouth 3 times per day, to throw up a water, swallowing random ships whole, she ATLEAST 50metres big, she look like...whillpool just not normal size..but there nothing more to tell about her look: she also cannot be killed, and meeting with her mean 50/50 luck..you can either survie without lost(if she won't open her jaw), or you can die and lost EVERYONE. Backstory: she also have 2 versions of story:
3. Again, monster sense birth.
4. She once a daughter of Poseidon and Gaia, beautyful sea nymph..who drown a sity for her father, so Zeus in anger transform her into beast. Personallity:..she just whilpool..no personallity, she hungry, she mindless, and brainless..but she extremly dangerous...she represent fear of greeks, of whilpools Powers: swallowing ships whole, moving sea, swallowing fish and GIANTIC MOUNTS OF WATER, she have scary size, she can't move, but she don't need it..