This is a small science project I tried when I wondered what would happen if a water balloon froze. (this is my first instructable, so go easy when giving comments.)
Step 1: Fill the balloon with water.
Fill the balloon till it gets to be the size of at least a basketball. then put it into a freezer droor.
Step 2: Freezing the balloon
When you take the ice out of the freezer, the water in the center will usually leak out. this means you did it right. it also gives it a see through appearance.
(freeze for at least 5 or 6 hours.)
when you go to freeze the balloon, make sure NOT to underfreeze. if you do, your ball of ice may crack and gush all over your freezer.
Step 3: Remove from freezer
when you remove the ice ball from the freezer, imediately bring the ice ball over to the sink.
A crack will usually form somewhere on the ball of ice, and water will leak from the center. If it doesn't leak properly try using some hot water to make a hole.
remove from freezer, and enjoy.