I might be too late to add this, but Rowing in Motion (my product) actually helps rowers analyze this using a smartphone's integrated accelerometer + gps. We can even live transmit the data to a coach following behind in the motorboat and overlay it (in realtime on the GPU) onto video footage captured from the camera.

See this video for a demo of the result https://www.youtube.com/watch?v=RdVSk3mA9Wk

And this article for an explanation of how the boat's acceleration pattern relates to rowing technique: https://www.rowinginmotion.com/optimize-your-rowing-stroke-w...

And this for an explanation of the math behind it (i.e. why certain acceleration patterns are more efficient than others and optimum technique will make you go faster): https://www.rowinginmotion.com/drag-efficiency-rowing/

Needless to say biomechanic analysis on smartphones is a ton of fun :-D