A ship-devouring monster in classical mythology, identified with a whirlpool off the coast of Sicily (9)
I believe the answer is:
charybdis
(Other definitions for charybdis that I've seen before include "monster" , "Mythical whirlpool" , "Whirlpool opposite Scylla" , "Whirlpool, across from 14" , "Scylla's counterpart" .)