There is a product called Brillianize. You should be able to find it at Home Depot or Lowes. If not, check with a company that sells plastic sheeting and supplies. Laird Plastics in Seattle is one of them in the NW. It is considered a plastic cleaner and polisher but it makes plastic slicker than $hi#. I spilled some on my linoleum floor and could have played hockey on it. I'm not sure how it will hold up to salt water but it might be worth a try. It comes in spray bottles and 1 gallon jugs.
Hope this helps.