While it doesn't feature couples falling off a boat, the film does have a scene where a couple is on a boat and a strong wave throws them off. It's a pivotal moment in the film as it highlights the challenges and risks associated with their lifestyle.
However, the movie is primarily about a group of radio DJs broadcasting rock and roll music from a pirate radio station on a ship in the North Sea during the 1960s.
Could you provide more details about the movie you're thinking of, like the year it was released, or any other specific scenes that you remember? This would help me identify the movie you're looking for.