Michael,
My suggestion is that you perform an experiment, and then give us your findings.
Try 1/60 for 10 seconds, double it for 10 seconds, and so on. Then compare the various looks that each one gives you. There is no right answer.
Having shot waterskiing before, I can tell you that at 1/60 you get nice white waterspray. At 1/500 or above you get water droplets for the spray.
John Lenihan
John Lenihan
LeniCam Video Productions