I spent a few summers on replica wooden sailboats from the War of 1812 (about the time Master and Commander is based on). you learn all kinds of knots working on period vessels. The ones I use(d) the most are Bowline, clove hitch, & taughtline hitch. Being able to "throw" a clove hitch over a post is a good skill to have when dealing with dock lines.

I also learned why sailors tend to be very good with knots. On some of my longer trips there wasn't much to do if you were not on watch so you practiced your knots and learned totally useless knots to pass the time.

For those of you who, like me, enjoy learning about knots pick up a copy of "The Marlinspike Sailor" by Smith. One of the best maritime knot books I have seen.