I think Mischa experienced ventilation. Ventilation happens when air is sucked down around the foil, and can happen to us on our A's/F16's/F18's/20's in high speed bearaways. Cavitation happens when the water boils because your creating so much lift on the foil sailing at high speed; pressure on the top surface is lowered and the water literally starts boiling (Chem 101).

Nice description: http://lancet.mit.edu/decavitator/Basics.html

Nice cavitation video: http://www.youtube.com/watch?v=DijdU0rmDdc