Water balloon physics

The rubber of the balloon creates up water pressure through the top hole, very much like a rocket turned upside down. This is what causes the ‘mushroom’ top to form, like the top part of a water fountain. Now for the second part. When water is in free-fall it is light. However, it is also passing through air that is stationary relative to the falling water. The effect would be like blowing a fan into a stationary, weightless sheet of water. This is precisely what we see. The ‘mushroom’ expands like its hit by wind, and then snaps into droplets.
These water balloon physics are forever pretty cool. It’s like the water makes a parachute and in reality catches air that breaks the surface tension. Very cool, it looks like an umbrella made of water.