a tarp?... comon... stop worrying about scratches, eventually you will get them and they make the ski faster too
I usually just beach up, and use a twist in stake to tie off from there so it doesn't wander away with the tide. I rarely keep mine overnight in the water unless we're planning a sunrise run, i'm not so busy that I can't hit the ramp to keep it on the trailer overnight. But if the ramp was really far or something, then sure i'd keep it moored.
if you can't beach it, then I suggest a minimum of two anchors, front & back, to keep it from wandering. If possible i'd also run a longer line from the ski to the shore and twist stake that. (that would make 3 tie downs and you'd be pretty safe that way)
my stake looks like this... I've only used it twice, it sucks for tying off in the water because you have to dive down to screw it in and my water is pretty dirty, no thanks, I only use it on the beach itself, and its pretty dam secure.
I have two anchors, mushroom style and again, only used them twice, ONE is not enough, if there is any wave action the anchor just gets pulled along. I never wanted to use danforth or car anchors, too many pointy ends inside my storage bin are a bad mix, I prefer the mushroom wrapped in a couple of towels.
