I use that yellow stuff I get at prepackaged at Ace but don't know if it's nylon or poly. I use it to secure my cages to the pier and I'd say it lasts for about two years. But it's not completely submerged.

I have a diffuser connected to a jug and it's been there for two years now.

If pigs could fly bacon would be harder to come by and there would be a lot of damaged trees.