Amanda Bynes -- Blonde Moment in Atlantic City Jacuzzi

And now ... "Where in the World Is Amanda Bynes?"

She's soaking in an Atlantic City hot tub -- or at least she was this weekend. Sources tell TMZ, Bynes checked in solo at the Revel Hotel ... where she stared into her phone while surrounded by strangers in the tub.

We're told she did pose for some photos with fans -- while wearing her famous blonde wig in the jacuzzi -- but if Amanda didn't like the way she looked, she demanded they be deleted ASAP.