So this is an idea I had while I was incredibly high. You know thoat inflatable donut things that kids have in pools? IDK what they are called, but if you got one of those, and then placed a pot with a plant on top of it, could you like, tie it to a tree, and place in on a lake? A lake wouldn't really run out of oxygen, now, of course, nutrients would be a problem, but I could find a wat around it, could it work?
Well lol now that is an interesting idea you have there. The floating device that you speak of does deflate eventually...but heck I'd like to see it done.