Being a retired(forced with broken back)licensed carpenter, I replaced my own floor. I used 3/4" pressure treated, below grade plywood, which we use on exterior studded walls that come in direct contact with the earth below grade. Really good stuff and much cheaper that marine grade plywood. On top of that I laid rubber ice and water shield, used for roofing, which has adhesive on one side.(added insurance) It was run 6" up each side of the gunnels to prevent water seepage at the edges. The rubber membrane also seals the screw holes that hold down the two sleeper seats. And then I bought a piece of exterior grade carpet, which was cut to fit and ran 8" up each side to cover the ice and water shield. A little bit of carpet contact cement holds the carpet tight to the gunnels over top of the ice and water shield. It's been in place for a few years now and is holding up great, and still looks great too.
A few notes though;
Marine grade plywood has a smoother surface, so if you're going with vinyl, it may be better so check them both out.
Ice and water shield is ultra sticky, so precut and prefit BEFORE you remove the paper backing. Start from the transom area and overlap each strip by at least two inches as you work towards the front of the boat. Once I have each piece ready to place, I cut the paper in the middle and start from the centre of the boat working my way out first to the left, then back from centre out to the right peeling off only as much paper as needed.
Lastly, I found that brown carpet is usually best if you're a fisherman. Why? Blood dries to a brown colour and isn't as unsightly over the long haul. I am usually spent by the time I get home after an outing, therefore I have never cleaned the carpet(just the
fish) in the entire time this carpet has been down and it still looks great after all those fishing trips with salmon and trout flopping at the transom.