Mike (Gilbert Roland) and Tony Petrakis (Robert Wagner) are Greek American father and son sponge-diving entrepreneurs who find themselves in competition with the Rhys family, Conch fishermen who are prepared to resort to violence and murder to maintain their established fishing grounds off the Gulf Coast of Florida. Run-ins between the two clans lead to an exchange of threats and all-out brawls. Further complications ensue when Tony Petrakis meets Gwyneth Rhys (Terry Moore), and the two fall in love