Although rowing backwards has found a following, circular rowing has never garnered a large number of enthusiasts. Consequently, there is no such thing as a sweep single. The normal configuration of a sweep boat has oars alternating from right to left, or starboard and port. Since there is no one to steer and not row, one of the people works the rudder with his foot while rowing. Not an easy task.
Eights always carry a coxswain.
The eight is the fastest boaton the water. An elite level men's eight is capable of moving at 13.2 mph. It Only Looks Easy. The whole body is involved in moving a shell through the water. Drive, Finish and Recovery.