じゃない and its uses


In a script I'm translating, two kids are reenacting The Little Mermaid at a
park and then one of the kids's mom walks up and says:
ちょ……ちょっとふたりとも何をやってるの！？ビショビショじゃない！

According to DeepL, this じゃない isn't a negative and I was wondering why.

