The film has an ensemble cast consisting of Philip Seymour Hoffman, Bill Nighy, Rhys Ifans, Nick Frost and Kenneth Branagh.

Seventeen-year-old Carl, recently expelled from school, is sent to stay with his godfather Quentin, who runs the station Radio Rock anchored in the North Sea.

In London, government minister Sir Alistair Dormandy resolves to shut down pirate radio stations for their commercialism and immorality, instructing his subordinate Twatt to pursue legal stratagems to accomplish this.

Quentin counters by bringing massively popular DJ Gavin Kavanagh out of retirement on Radio Rock, enticing advertisers to pay their bills from abroad.

The Count challenges Gavin to a game of chicken in defence of Simon's honour: The stubborn rivals climb the ship's radio mast to a dangerous height, but reconcile after they are both injured jumping into the ocean.

Twatt proposes the creation of the Marine, &c., Broadcasting (Offences) Act 1967, making pirate radio stations illegal on the grounds that they endanger communication with other vessels.

Despite heavy public support for the pirate stations, the act passes unanimously through Parliament and takes effect at midnight on 1 January 1967.

Additional minor roles were played by Ian Mercer as the transfer boatman, Stephen Moore as the Prime Minister, Michael Thomas and Bohdan Poraj as Dormandy's subordinates Sandford and Fredericks, and Olivia Llewellyn as Marianne's friend Margaret and Felicity's love interest.

[11] Filming took place on the former Dutch hospital ship Timor Challenger, previously De Hoop, moored in Portland Harbour, Dorset; the "North Sea" scenes were shot off the coast of Dunbar, East Lothian.

[16] The official synopsis of The Boat That Rocked before release stated that it tells the fictional story about a group of DJs in 1966 who are at odds with a traditionalist British government that prefers to broadcast jazz.

Upon the release of Pirate Radio in the United States, Manohla Dargis wrote:[21] Stuffed with playful character actors and carpeted with wall-to-wall tunes, the film makes for easy viewing and easier listening, even if Mr. Curtis, who wrote and directed, has nothing really to say about these rebels for whom rock 'n' roll was both life's rhyme and its reason.Robert Wilonsky, reviewing Pirate Radio after having seen The Boat That Rocked and its UK home video release, said the U.S. theatrical release had had "most of its better bits excised"; according to Wilonsky, "after watching the DVD, Pirate Radio feels so slight in its current incarnation.

The trailer in North America also featured dialog from a scene not in the release; chief among which were a British government minister was being told in a voiceover that the American deejay "The Count" is "possibly the most famous broadcaster ever," which wasn't borne by the actual plot.

"[27] The Hollywood Reporter ran the headline "Rock 'n' roll movie Boat just barely stays afloat," declaring the film too long to sustain interest.