Kind of a second on the sand anchors. (I say kind of, because I don't have one!) But, I do have a huge metal one, and I think the sand kind would work alot better. But, I have seen the sand anchors, and they are the best, for this application, as I see it.
One main advantage is you can place it back in teh "Trunk" on the sea doo, and not tear up the fiberglass. You can ride across the lake with it in the trunk, and not tear up the fiberglass.
And, if the rope is long enough, then the angle of pull is reduced alot. Too steep of a rope, in big waves, I think it will move.
So, my suggestion is a longer rope for the big waves, and a nice big sand bag one. Maybe as big as a 5 gallon bucket, made of canvas, or some tough material.
We usually park ours near the swimming area, so the kids can swim, and hold on the ski, and jump off the ski, and play, so the big chunk of iron works for me. But, I'd prefer the sand bag.
N