... so excellently in material functions, but cheaper.2), generally, how long can people stay in the water ball?a). ... air inside the ball at least every 30 minutes3), HOW DO YOU GET INSIDE OF THOSE BALLS?We have ... a zipper!4), HOW DO I BLOW THEM UP?Use an air blower. ... .8),"WATERBALL JOGGING"This is one of the best ways to build up your strength, balance, endurance, and its fun, ...