The first time graduate student Renea Ruffing actually saw the bulgy-eyed invaders from Eurasia, she was scuba diving near Erie, Pennsylvania.

“We swam over a rocky area, and it was unbelievable,” she recalls. “It seemed like there were millions of them, covering the bottom as far as you could see, all looking up at us with those unblinking eyes. I’ll never forget the sight. Most people don’t fully realize the scope of the goby invasion—it’s enormous!”