On the water, you don't reposition
At the edge of a pitch, a photographer can move between plays. On a regatta, the vantage point is fixed at the start: once the race is under way, moving takes longer than the race itself.
So everything is decided beforehand. Knowing the course, where the tacks will happen and where the boats will bunch up determines what you'll be able to film, and what you'll have missed for good.

