Humiliate them

"... strip. We'll practice in the nude from now on."

The girls groan, but take off their swimsuits. Now they all try their best to cover up.

"And don't cover up! If you cover up, you feel embarrassed! Therefore I will throw everyone, who covers up off the team! Oh, I almost forgot: Don't let the spectators bother you!"

The girls turn around and look directly at their spectators. They can't believe what they're seeing.