Master and Commander
It's one thing to think about sailing on the high seas and to romanticize the tactical battles between ships, but the reality, I imagine, would be quite a bit different. This movie conveys some of the brutal reality of what it must have been like to sail aboard a ship in the 1700s better than any movie I've seen. The best thing, though, is that it really does it almost in a matter-of-fact manner, as the crux of the story revolves around the relationship between the captain and the ship's doctor, played by Russell Crowe and Paul Bettany, playing off each other as well as they did in A Beautiful Mind. This is a very good movie.