The Hammersley attempts the daring capture of an illegal fishing ‘mother ship' but is thwarted by violent eco-terrorists. Mike finds himself falling in love with beautiful marine biologist Ursula Morrell, who later goes missing under mysterious circumstances.

The HMAS Hammersley confronts a series of new menaces in the northern waters from pirates to toxic crabs, not to mention a gorgeous solo yachtswomen with a rescue fetish.