Differences in Raft Speed
Most of the paddle strokes that a paddle raft crew takes to steer the raft propel the raft forward. Therefore paddle rafts move down the river faster than other rafts. Self bailers are next fastest. Fully loaded self bailers carry a lot of momentum and offer a lot of surface area to the river. So friction with the water causes them to be dragged along easily by the current. Since it's a lot more work to fight against these factors, the steering strokes that the person at oars takes are usually forward strokes.
The raftman just tries to adjust the direction or vector of the rafts natural movement down the river during Colorado River Rafting. It may be surprising to know that catarafts are usually the slowest at traveling down the river as they offer less surface area for friction and are so light that it is easy for the oarsman to pull back, arresting the momentum. For these reasons, rookie oarsmen in catarafts are usually at the back of any group of rafts.