Destroyed stuff always drop their materials, no matter who or what destroys it.

but just a couple days ago I was out sailing and had bad fog roll in and got beached unfortunately in the plains right in front of a fuling base.

That's nightmare fuel that is, lol

When I say stuff in the water despawns quickly, I mean relatively. Stuff on land seems to hang around for days. When I threw stuff into the sea they were gone in a day I think.