Keelboat

This 50- to 75-foot-long ship is 15 to 20 feet wide and has a few oars to supplement its single mast with a square sail. It has a crew of 8 to 15 and can carry 40 to 50 tons of cargo or 100 soldiers. It can make sea voyages, as well as sail down rivers (thanks to its flat bottom). It moves about 1 mile per hour.