Mark Rober teamed up with The Backyard Scientist to see what happens when you fill a pool with 25 million water balls then try to jump in.
After determining that jumping in puts jumpers in about chest deep, they open up the pool to Mark's nephews and have a blast the rest of the time.
Water balls, or jelly beads, are a lot of fun if you haven't played around with them. This starter pack will make about 40 gallons of beads.
• 25 MILLION Orbeez in a pool- Do you sink or float? (YouTube/Mark Rober)