P.J. Wilson rescues a fellow traveller, McNeill, who is washed overboard on the journey from Broome to Perth. P.J. is rewarded by McNeill with a loan for shares in a pearl lugger and a map showing a prosperous oyster reef.
P.J. returns to Broome and joins the company of the Wanderoo to fish for pearls. In a life and death struggle on the ocean floor, P.J. must battle a giant clam, a Diamond Fish, and McNeill's untrustworthy Malay servant, Sharkey, before he can claim his fortune.
