Waterproofing soldering in 5085

So, i want to build to build a small “tow” kit for a wingfoil spot that is a couple hundred meters in a wind shadow. So as long as it moves me that distance, even at turtle speed, its ok

The flipsly 5085 looks great, but i have no idea how to waterproof the solders. Any tips? Thanks!

24 hour resin? If its fresh water i would just silicon it or something light