For those of you who have never heard of the tv show and are just wondering what these balls are, well basically around a few lakes in Hanoi you can rent these things and go float on the water. From what I can tell their purpose is two fold:
1. The majority of the people in Hanoi can not swim so this is their only way to get out on the water.
2. You would NEVER want your body to actually touch the lakes/rivers/streams in Vietnam which are highly polluted.