Unfinished cypress swing

You don't need to seal it at all.

You’ll regret using poly on cypress for the exterior application. It’s going to look great for the first year but start to look like junk the years following and get worse. My vote is let it age naturally. If you are adamant, I’d use some sort of oil.

McCloskey Man O War Marine Spar Varnish


But you will still have to sand and redo every few years

I just pressure wash mine every couple years and it looks good again for a couple years. Mine will be 19 yrs old next summer.