An Australian Navy Patrol Boat, the HMAS Hammersley, is casting off with a new crew. Among the crew is Commanding Officer Mike Flynn and Lt. Kate McGregor, who went through a nasty break-up. Will Kate be able to serve under Mike? How will their personal problems affect the rest of the crew?

The crew of the Hammersely sail into trouble when they uncover a drug smuggling ring, and Mike is convinced the police are covering up the murder of a marine biologist.

Mike faces a dilemma when he's forced to choose between saving a missing refugee or helping two of his crew who have been stung by a deadly jellyfish.

The crew attempt to capture an illegal fishing ship, but are thwarted when eco-terrorists get there first, and Mike is puzzled when a beautiful marine biologist goes missing.

The crew almost collide with a floating shipping container, and receive a shock when they discover it's full of North Korean refugees. Meanwhile, Kate falls for a civilian sailor.