Captain Cain is the commander of the Alerte, a pirate submarine, pursued by the HMS Canvey. It is damaged and sinks in a shallow West African Lagoon where Cain and a select few escape the vessel in diving suits. Arriving ashore they steal a whaling craft from an unsuspecting fisherman and join a Greek Ship heading for Paraguil del Norte wher the pirates become embroiled in a local war.
A sequel to The Pirate Submarine