POSSIBLE PLOT SPOILERS!!!! Hypnotist Dr. Lombardi (Chester Morris) puts his assistant Andrea (Marla English) into a deep sleep. When this happens her thing in a past life (the title creature) comes out of the sea and kills people. Lombardi knows this and "predicts" the killings. Dr. Ted Erickson (Lance Fuller) thinks Lombardi is a fraud and tries to prove it. He also falls in love with Andrea which bothers Lombradi a LOT....
Absolutely ridiculous story but this isn't a total bomb. Some of the discussions on reincarnation and past lives are interesting, there's good direction and a really eerie music score. Also the creature itself has become one of the legends of horror movies. It looks pretty scary and has HUGE breasts!!!! You just have to laugh when the creature attacks people--and they just stand there and do NOTHING so it can kill them! The acting wavers. Fuller seems to be (wisely) kidding the material but isn't bad. Morris is VERY serious (and dull). English is just stunningly beautiful and very good in a tricky role. Tom Conway shows up in a small role and has fun with the material.
So--this has its good points but the silly story and slow pace really wears you down. Worth catching at least once for the monster. I give it a 3.