Wikipedia
Drift boat
A Drift Boat is an evolution of the open-water dory, converted for use in rivers. The design is characterized by a wide, flat bottom, flared sides, a narrow, flat bow, and a pointed stern. A Rocker is used along an arc from bow to stern along the bottom of the boat. It is this constant rocker that allows the boat to spin about its center for ease in maneuvering in rapids.