I suspect those Vegas pools were concrete so bonding the water was not an issue. The water was a conductor and bonded everything in contact with it, where fresh water might not. Tesla is talking about a plastic tub, where the water is at a different potential than anything around it. If everything remains non-conductive for 5 feet or so around the tub, there is no real problem. If you have a grounded tile floor, you are going to feel that shot, even if it is just static electricity.
I bet, if you did nothing but punch a stainless bolt through that tub wall, in contact with the water and bond it, you would be fine.
680.26(C) says you should have 9 sq/in. tho
