It is difficult to determine who is the more ferocious character in this film: The real shark seen in the underwater sequences, or star Edward G. Robinson. Robinson plays a Portuguese tuna boat skipper--the self-styled "best dam' fisherman in the Pacific"--who years earlier had lost his hand to a shark while rescuing best friend Richard Arlen. Robinson promises to look after the daughter (Zita Johann) of a recently deceased crew member. He proposes marriage; she accepts, more out of gratitude than love. The girl eventually falls for Robinson's pal Arlen, who wants to break off the relationship before Robinson gets hurt. But Robinson catches the lovers together, and vows to kill Arlen. In attempting to throw his ex-friend to the sharks, Robinson is accidentally pulled overboard to his own death. Warner Bros. would unofficially remake Tiger Shark several times over the next ten years; while the professions of the two leading male characters would change, the basic "triangle" plot remained the same.
by Hal Erickson synopsis