Course clean up at the San Diego Crew Classic

We wondered what this boat was doing when we first saw it.  There was a man in the front holding onto a huge red rake -- a leaf rake on the water?   We kept an eye on him as he slowly moved up & down the course.  Finally saw the reason:  course clean up!   Probably the most thankless job of the day!   But a very critical job --  if these clumps of seaweed got on the course they could slow a boat down.