Set aboard HMAS Hammersley, an old Royal Australian Navy (RAN) patrol boat, the series follows the ship's company as they are seen investigating the deaths of several people who are linked by a web of intrigue.

Most of the footage was shot aboard the patrol boat HMAS Ipswich, with up to 60 cast members, film crew, and ship's company.

Ratings for the first episode were the second-highest for a drama premiere in Australian history and surpassed the NRL State of Origin match earlier in the week.

Initial reviews were mixed, with a concern that the series would be restricted by the early time slot, poor scripts, and clichéd characters and storylines.

The first season story arc involves the Australian Federal Police's investigation into the death of marine biologist Dr. Lisa Holmes, Kate's relationship with freighter Captain Rick Gallagher, Mike's relationship with Lisa's partner, Dr. Ursula Morrell, and the deaths of two fishermen, Carl Davies and Sam Murray.

These threads increasingly intertwine throughout the season, culminating in the final two episodes, in which it is revealed that Gallagher hired Ursula and Lisa to manufacture a deadly toxin from an unusual venomous crab that he planned to sell on the black market.

The plot is thwarted, the boat carrying the poison is sunk, Gallagher is killed and Ursula's death is staged as she enters a witness protection program.

During the season, Nav and ET develop a relationship despite adversities: Chefo gets engaged to his girlfriend; Swain's wife, Sally, gives birth; Charge reluctantly gets help and recovers from an eye injury; Spider loses friend and shipmate Jaffah to a jellyfish sting; Robert comes to terms with his father's death; and Lt. Daryl Smith has a mostly off-screen and implied relationship with AFP Agent Alicia Turnball.

Hammersley answers a distress call from a marine biologist on Bright Island, and they release the FFV under its own steam and the care of ET and Jaffah.

Whilst on the Island, newly arrived Able Seaman Bill Webb, "Spider", who is suffering the effects of seasickness, meets up with two fishermen.

Still very naive and new to Navy life, Spider is delighted to accept a gift of fresh crab the fishermen have recently caught, and returns the catch to Hammersley to share with his ship mates.

Back on the FFV, the fishermen are making dinner and accidentally set their vessel alight and its crew, with Jaffah and ET, are forced to abandon ship.

When Hammersley arrives back at base, the CO discovers that the Australian Federal Police (AFP) are very interested in the death of the marine biologist, Lisa Holmes.

While transporting AFP officers Greg Murphy and Alicia Turnbull to Bright Island, Hammersley encounters a sophisticated buoy.

Hammersley pursues the suspected pirate boat and, when they board it, find it to be barely seaworthy; the 'pirates' are a family of terrified illegal immigrants attempting to reach Australia.

The flare fired by men on the other boat has injured one of the immigrants, while attempting to help them by transferring them to Hammersley, they are scared and throw a bucket of waste water at the crew.

Charge fears that his injury may cause his career aboard patrol boats to end, and that he may be forced to accept an office job.

Returning to port following a successful mission, Mike finds that Dr Morrell has moved house and has left no details.

Two friends aboard a luxury boat have also come across the container, and when met by Hammersley, the crew realises that these are the men who gave Spider the crabs on Bright Island.

Hammersley receives an emergency signal from an EPIRB and, upon investigation, finds a young female sailor who claims she has been attacked by pirates and forced from her yacht.

Hammersley manages to track down the pirates and attempt an interception, but they are forced to return to shore when members of the crew start to suddenly fall ill with severe food poisoning, caused by the crabs (the ones gifted to Spider on Bright Island).

Hammersley returns to normal duties, and during an attempt to intercept an FFV, another mayday call is received, again from Claire Watts who is supposedly being attacked by the captured pirates.

Just off the coast from Bright Island, Hammersley intercept what appears to be a suspicious meeting of two boats at sea, but they discover too late that they have in fact interrupted a sting by the Feds into diamond smuggling.

Swain has been given time off to attend the birth of his first child, that is, until his replacement gets the flu, and Hammersley is tasked with rescuing a teenage couple who appear to have run out of petrol.

The girlfriend of the rescued teenage couple is heavily pregnant and goes into labour on the boat, and it is discovered that the boyfriend has escaped prison to be with her for the birth.

The crew risks life and ship to hunt down the rogue terrorist boat, Pacific Mariner, and retrieve or destroy its cargo of bottled water containing the biotoxin.

Mike is forced to make the most difficult decision of his career when he orders his crew to open fire on the rogue ship, knowing Ursula is being held hostage on board.

Sea Patrol's premiere drew a larger audience than the NRL State of Origin match broadcast the same week, a rarity for an untested local drama.

[5] With a theme worthy of James Bond and glorious footage of our coastal waters and shores, Sea Patrol sweeps over you like a well-made feature film.

It looks terrific and, despite a certain predictability in the set-up and character types and some unlikely touchy-feely stuff nestled amid the blokey banter...there's enough going on to ensure viewer appeal...[A] cracking beginning to a promising new show.While the critical response improved, ratings continued to drop throughout the season.