[jasonwatkinspdx]

Well, these have a keel that generally keeps them upright. It's almost certain they've been designed to be self righting if they do get knocked over by a breaking wave. Likewise, they float, so temporary submerging shouldn't be much of a problem provided they're sealed well.

One advantage of this kind of wing sail is it's "self trimming". With the tail/tab in neutral position, it'll always weathervane to follow the wind. With the tail tab deflected somewhat, it'll weathervane with some amount of angle of attack. So even in very heavy winds, all it needs to do is back off on the angle of attack and it should be in a relatively stable state.