For water work, given my druthers, I'd go with something other than nylon- it is heavier than water. :P I've got some marine utility cord, braided, about as thick as p-cord. It floats, I think it is polypro but I'm not sure. I got it for a lanyard project, but it is at my folks in my braiding box.
Was more of a what-if thought as opposed to an actual need.
