Which leisure activity involves using a small open boat to travel on a river?

Canoeing is the leisure activity that specifically involves using a small open boat to travel on a river. In canoeing, participants typically sit on their knees or on a low seat within the canoe and use paddles to propel themselves along the water. This activity is often associated with rivers due to their calm and scenic nature, which makes them suitable for exploration and enjoyment.

The other activities, while they do involve water and boats, differ in terms of the type of vessel used and the method of propulsion. Kayaking involves a closed vessel designed for one or two paddlers, making it distinct from the open design of a canoe. Rowing typically uses longer, more stable boats with oars, which is a different technique and style of movement on the water. Sailing utilizes larger vessels equipped with sails rather than paddles and is commonly associated with open sea or large bodies of water.