Hull skin

Has anyone used or know of a skin to protect your hull from scratches rock and shoreline damage?

Passed a guy on the freeway and his ocean kayaks had a coating or skin applied to the hull

rotomolded kayaks?
I assume you are talking about rotomolded plastic kayaks (which are generally made with a form of polyethylene plastic). This is the most common type of fishing kayak, but there are some thermoformed and even more rarely, composites.

For rotomolded, there really isn’t much you can do. Not a lot sticks to it, so adding a coating just doesn’t work. That said, rotomolded kayaks are also very rugged, so not a lot needs to be done. Scratches are generally cosmetic only, not impacting performance of boat.

Some makers put in screw or bolt on replaceable plastic sections at high wear areas (like where a boat would get dragged).

High end kayaks usually have covers available, but they are awkward for most kayaks.

I have an Ocean Kayak Terra that rode the top of my pop top camper to the ground and slid down the road at 55mph upside down. I just pulled out the sand paper and trued up the fuzz on the scratches, repaired the cut straps and its been fine ever since. Don’t worry about it. You can also use a heat gun to soften the scratches. But don’t over heat the plastic.