Try to find a Non Slip High Gloss varnish or Sealer for external use! Ask at your largest DIY for help!
John avallance82 is right on the money. I would recommend using (spar varnish’. It was originally designed for use on boats, so this tells you that it will hold up well with the weather. Make sure to use spar varnish that is made for floors.
Yeah marine spar varnish is the way to go for exterior jobs.
Hi Bob, this is a video of a wet look product, with instruction for applying it