A successful tuna fisherman has bad luck with women and sharks in this realistically filmed melodrama.
Captain Mike Mascarenhas (Edward G. Robinson) and two other men are lost and hungry in a lifeboat as tiger sharks swim around. In desperation one of the men attacks Mike and is thrown overboard and killed by sharks. Mike also gets his hand bit off but saves his friend Pipes Boley (Richard Arlen). Mike is getting record tuna catches but is not having much luck with the ladies. Manuel tells him he may not get into heaven missing a hand. Later Manuel falls in the sea and is killed by a shark. Mike catches the shark so that Manuel can be buried with all his limbs.
Mike visits Quita ((Zita Johann) to tell her of her father's death. He comes back with food and wine, giving her "insurance" money she knows he is lying about. She fixes him breakfast, and they become friends. When a man refuses to leave and tries to kiss Quita, Mike comes in and stops him. Mike asks Quita to marry him. She says she is not in love with him, as she is still suffering from a man having walked out on her. Yet she agrees. Mike asks Pipes to buy a wedding dress, and he takes it to Quita. Quita explains she is marrying Mike, because she is so grateful to him. After the wedding at the party Mike does not dance and asks Pipes to dance with Quita while he gets drunk and goes to sleep.
After three weeks of fishing Mike greets Quita and oversees the unloading of the fish. While Mike is frying fish at a campfire, Quita tells Pipes she is in love with him and can't go on with Mike. At sea Pipes tells Mike he is going to leave on a freighter. Men pull in tuna with poles while Mike coaches them. Pipes gets a hook stuck in his neck, and Mike returns the ship to San Diego, taking Pipes to his home and a doctor. Quita nurses Pipes for six days; then he is ready to go to sea with Mike. Quita wants to go too. While Mike is shooting at sharks, Pipes tells Quita he won't do anything with her but that it is better if he leaves. She says she loves him, and they embrace; Mike comes in and knocks Pipes unconscious with his artificial arm. Mike locks in the men and drags Pipes into a lifeboat, which he proceeds to scuttle, saying he is returning him where he found him. A rope trips Mike into the water; he swims and is followed by a shark before he is pulled out. He says he gave himself for bait twice. He hopes to be remembered in song and dies.
The fishing scenes are real, but it is jealousy that leads to Mike's tragedy in the age-old triangle. Whoever can distinguish the soul from the body knows that a maimed body cannot tarnish the immortal soul.