might be level, but ground usually isn't.
So, a laser set on the ground won't mean the boat is at the right attitude.
I know(or have heard), that when boats are put on the hard
, the stern is left lower for drainage . . . so a level might not work, although a laser set at the right level and adjusted to meet the "proper", waterline in a few places should work. Just make sure that you get the same results on both sides.
What I did, was to NOT have the boat pressure washed when it was hauled.
I'm a surveyor
, so I had previously measured the entire boat.
So, all I had to do was take photographs of the waterline(sludge line), and I'll use those measurements as the basis to move my waterline . . . if I do.