Do water balloons float or sink in water?
They float because the rubber membrane makes them slightly less dense overall than water. If you place a balloon filled with fresh water in a tub of fresh water, it will float due to the rubber membrane making it slightly less dense than water. However, if you salt the water that fills the balloon or if you fill it with dirty mud, then you can make it sink in water, and it can still be a “water balloon” which does indeed sink in water. So, to be very devious, you can fill two identical balloons, one with fresh water and one with a salted water, and not tell anyone which is which… then try having your wife guess which will float and which will sink.
