Around 50kn of water flow around a wing in normal sea-level pressure levels (or fin, that is why the speed kiteboarders are stuck at exceeding this same speed number) the pressure drops so low that the boiling temperature of water is equal to that of the ambient water. This results in a sudden loss of flow along the surface.
That means no lift of grip any-more..
Sailrocket from Vestas appeared to have this issue with the fin only, as this machine skimmed the surface and party hovered above the water.
They claim to have solved it by changing the fin type during the ride from conventional wing profile into a so called super cavitation version.
Basically a wing section with the trailing edge being sharp flat.
Powerboats use these also with their propeller blades for the same reason:
(the rear of the propeller is upward, so you clearly can see the straight, sharp edge)
That is what I understood reading about this.
Here is a small article about cavitation and sailrocket
And here a more detailed story
Disadvantage for sailing craft (versus mechanical horsepower) is the excessive drag at lower speeds: no chance to reach the top speed then.
This is a nice engineering challenge for the near future I guess