A good mount can help you move more quickly through the wilderness, but its primary purpose is to carry the gear that would otherwise slow you down.
Keelboats and rowboats are used on lakes and rivers. If going downstream, add the speed of the current (typically 3 miles per hour) to the speed of the vehicle. These vehicles can't be rowed against any significant current, but they can be pulled upstream by draft animals on the shores. A rowboat weighs 100 pounds, in case adventurers carry it over land.