By Dan Plante / Yahoo KUSI / Wed, July 22, 2026 San Diego Bay was once considered among the most polluted waterways in America. That was then; this is now. According to environmental watchdog San Diego Coastkeeper, the Big Bay is bouncing back in a big way. "We did water quality testing for an entire year at different locations around San Diego Bay. We were all a little surprised at how clean it is. I would actually go swimming here. San Diego Bay is cleaner than Mission Bay right now," said Phillip Musegaas of San Diego Coastkeeper. It's taken decades to reach this point. At one point in history, the bay was an open dumping ground for industrial waste. Since then, tons of toxic sludge and solid waste have been dredged from the floor of the bay.