As I understand it, you can only move up one boat at a time. When you bump someone those two boats are taken out of the water.
I guess there is a winner in that after each race either the boat in front is still in front or else the second place boat caught up and is now the leader. I think the goal is to stay in front for as many years in a row as possible.
Sounds like it could be fun, but it doesn't seem like a good method for determining who rowed the fastest this year. Depends what the goal is.