On the beautiful island of Samarang, in the Malay Straits, the natives of a small village depend on the ocean's bounty for their livelihood. The ocean is both provider and destroyer, for although the people cannot live without the fish and pearls for which they dive, they are often killed by sharks, octopi and other dangerous creatures. Mamounah, a venerable matron, relies on her sons, the brave Ahmang and fun-loving Ko-Hai, for support after all of her other relatives have perished in the water. Ahmang is in love with the vivacious Saiyu but has little hope of marrying her, for he is poor while she is a chieftain's daughter. Desperate to earn enough money so that he can marry Saiyu, Ahmang decides to sail on the ship of crafty Chang Fu and dive for pearls. Half of the male population of Samarang has been lost because of primitive pearl diving methods, and Chang Fu makes the excursion more risky by going near the island of Sakai, which is inhabited by cannibals. Chang Fu promises Ahmang his best pearl in exchange for help procuring other divers, and Ahmang agrees. Before the ship sails, the natives watch the ritual "Shadow Show," in which performers warn the divers of the perils that await them. Ko-Hai, who is excited at being allowed to go on the excursion under his brother's protection, is heartbroken when, during the show, his pet mule-deer wanders off and is killed by a python. When the ship sails the next morning, the stoic Mamounah watches as her sons and Saiyu leave. Later, all appears to be going well as the ship anchors near Sakai, and the diving begins. Ahmang finds a large pearl, and the others also do well. Catastrophe strikes when they run out of fresh water and are forced to go ashore to search for more. The searchers are attacked by cannibals, and while most of them escape, Ahmang and Saiyu are left behind in the confusion. Eager to claim Ahmang's pearl for his own, Chang Fu gives the couple up for lost and sets sail. Although they are frightened by the wildlife, Ahmang and Saiyu make friends with an orangutang and find food. Chang Fu is forced to return to the island by the crew, and Ahmang and Saiyu are rescued. While everyone is rejoicing, Ko-Hai, determined to be as good a diver as his brother, jumps into the water. Saiyu sees a shark and alerts Ahmang, but despite Ahmang's attempt to save him, Ko-Hai is killed by the shark. The entire population grieves when his body is brought back, and Ahmang becomes obsessed by thoughts of revenge. Soon after, Ahmang and Saiyu return to the ocean and Ahmang kills the man-eating shark. By avenging his brother's death, Ahmang has proven his bravery, and soon receives permission to marry Saiyu. A happy Mamounah helps Saiyu prepare for the wedding and everyone enjoys the ceremony.