Make the surface area as big as possible. You can just fold the edges up so it looks like a square plate with its edges folded up.
Depends on how big you make it.
I don't think anyone knows the answer to that and never will.
"There is no way that someone has gone around and counted all the boats on earth." Wow, people with the most basic of thought should disregard this morons answer. If one could request all vessel...
because tin foil is less dense then water so it makes it float!!!!