There are 3 different types of races scouts can participate in. First is a relay. This means that scouts will have to switch out of the boat while others get into that same boat. The second and third types are endurance/sprints. These are both similar in that the same 2 people stay in the boat the entire duration of the race.
Relays - 4 girl relay, 10 miles, 1 switch - 6 girl relay, 15 miles, 2 switches
Endurance - 15 miles, 2 people the whole way - 10 miles, 2 people the whole way
Sprints - Division 1, 5 miles, 2 people the whole way, ages 11-14 - Division 11, 5 miles, 2 people the whole way, ages 14-18
Please Note - Scouts can race up a level if needed but cannot race down
Source - GCCR race results from about 2010