I remember that was the big deal for Sailrocket to go beyond 50ish knots. Traditional foils hit a wall since beyond that speed, they would cavitate and the increase in drag and loss of lift was almost insurmountable.

Here's a good write-up and some pictures of what the super-cavitating foils look like

http://chevaliertaglang.blogspot.com/2012/12/clearing-50-knot-gate-hydrofoil.html

and another (about 2/3s the way down)

http://www.realisedesign.co.uk/product-design-blog/2012/fastest-boat-sailrocket-sailing-speed-record/

It's more a wedge than a wing shape we usually thing about. The bubbles behind the wedge effectively become the trailing edge of the foil.

I think I read somewhere that about 46 windsurfers had signed up for runs at Luderitz this year. Pretty busy.

I'd be remiss if I didn't include Sailrocket's own discussion of the foil but it lacks pics

http://www.sailrocket.com/node/288