Decided to replace floor - best paint / sealant to use?

I just started the process of converting my 7x16' V-Nose cargo trailer and while removing all the wall boards to add insulation I discovered there are a few leaks (purchased trailer used). No big deal but I felt some flex in one of the floor boards about the same time and got the itch to pull the one furthest back up.. It seems to be in fairly good condition but while I'm going wild with this conversion, I might as well replace all of them. This also gives me an excuse (access!) to do a lot of mods under the floor..
That being said, I know I need to seal / weatherproof the bottom side of the new floor. Is there a specific product that you all recommend?
Thanks,
David
That being said, I know I need to seal / weatherproof the bottom side of the new floor. Is there a specific product that you all recommend?
Thanks,
David