Doing It for the Art: Peter Weir insisted that the production use real cannons firing actual gunpowder charges in order to show realistic recoil and to capture live audio rather than using recorded cannon noises in post production. Weir experienced permanent hearing loss that he attributes to his decision.
Dyeing for Your Art: Jack Aubrey is supposed to be quite stout, and Russell Crowe attempted to gain the necessary weight but found that he couldn't, so the film had to settle for a captain who was slightly overweight. Crowe and Paul Bettany also learned to play the viola and cello, respectively, so that they could be filmed performing the proper bow and finger techniques.
Enforced Method Acting: Much of the filming was done onboard the Rose, a modern replica of the 18th century frigate HMS Rose, which was a semi-contemporary of the real HMS Surprise. All actors were given a crash course on 18th century sea-faring. Also during rehearsals, all actors were given tags based on whether they were officers or sailors. This enhanced the sense of camaraderie within each group, and made sure the actors felt that officers and sailors should not mix. Officers' actors were also given a nice clubhouse to rest in throughout the filming. Notably, Paul Bettany was the only one out of both cast and crew to never get seasick (he had quite a bit of boating and diving experience already).
Executive Meddling: Russel Crowe and Paul Bettany learned how to play violin and cello for their respective roles, but were dubbed over in the final cut with professional recordings.
Fake Brit: Jack is an Englishman played by an Aussie.
Stillborn Franchise: The film adaptation had nearly the entire cast signed on for multiple sequels, and they bought the actual boat they used to make sure it was going to be available. It made enough money to be deemed a financial success, as well as being well-received critically, but not enough to make the sequel a sure thing, and in the end it never happened. The principal cast have all said over and over that they'd love to do more, and so has Peter Weir. Weir just tends to take a long time in between his projects. He also said that shooting a film on water is the hardest thing a director can do, and thus he'd really need to be sure that it'd be worth it.
Of a sort. The French frigate is represented by a 3D model of the USS Constitution, an American (nominal) 44-gun Heavy Frigate (essentially an Age of Sail Battlecruiser). note Though rated at 44 guns, the USS Constitution invariably mounted 56 guns, not counting chasers. Most of these cannon are long-barreled 24-pounders, while the rest are even larger, short-barreled carronades. The reason for the discrepancy is that a ship was rated by how many guns it was launched with, not the number it eventually mounted, especially in the case of carronades added after commissioning. In The Far Side of the World, the book the film was based on, the enemy was the USS Norfolk, a 32-gun American frigate during the War of 1812 more comparable to the HMS Surprise, based on the Real Life exploits of the USS Essex.
The Surprise herself, portrayed here by the replica of the HMS Rose, a 20-gun post shipnote A sixth-rate frigate with enough guns to warrant command by a post captain mounting nine-pound long guns. The Surprise, classed as a 28-gun sixth rate, was rearmed with twenty-four 32-pound carronades along her main deck plus eight 32-pounders on her fore- and quarterdecks, plus chasers, upon entry into British service. As in the French Navy, this caused confusion over whether she should be rated as a fifth rate or a sixth rate (she was re-rated as a sixth rate in 1798 and maintained this for the remainder of her career). She also bore the main mast of a 36-gun frigate, equally as inordinate as her heavy armament.