The more rounded the bottom, the less initial stability but the swifter the hull. Lake canoes should have a keel or v-bottom to help the canoe track and river canoes should not have a keel, for maneuverability. The greater the displacement, the greater the carrying capacity. This allows the paddler to heel the canoe over to carve turns which is important for whitewater boats. Tumblehome is also found in some recreational hulls.
Rocker is the amount the hull curves from bow to stern.
Rocker slows hull speed and decreases the accommodation of large payloads. Lake and touring canoes should have conservative amounts of rocker to increase hull speed. The bow is what cleaves the water, so it is important that the shape suits the use. Whitewater boats need high volume bows and sterns for buoyancy assuring their ability to go over large waves and giving the canoe more buoyancy over shorter lengths. More rounded ends in whitewater playboats make it easier to change direction in upstream maneuvers as well.