A movie about a guy that catches a ride on a ship with a caged mysterious beautiful woman. Unknowingly to him, she is caged becaused she turns into a man-eating sea monster at night and her beauty is to lure seamen to their death.:eek:

Maybe this one...

Mermaid Chronicles Part 1: She Creature (2001) (TV) (http://www.imdb.com/title/tt0274659/)