That's what I was thinking. The problem on or near land wouldn't be staying afloat (which I assume a ball like structure would manage) but surviving crashing in

That's what I was thinking. The problem on or near land wouldn't be staying afloat (which I assume a ball like structure would manage) but surviving crashing into structures and other floating debris. Wood seems to be a less than ideal choice for that. Perhaps a metal ball would dent but not break/leak like I'd expect wood to. But it looks like the maker has given this thing a lot of thought, so there's probably something I am missing.