Why Can't You Swim in Most of the Bay Area Lakes?

The Bay Area is defined by water. Not just by the bay itself, but by the Pacific Ocean and myriad rivers, reservoirs, lakes and ponds. Yet most of the bodies of water you drive past are devoid of people. No swimming. No splashing around. Not even on the hottest days. Why is that? Additional Reading (including a list of where you can swim): Why Can’t You Swim in Most Bay Area Lakes? Reported by Kelly O’Mara. Bay Curious is made by Olivia Allen-Price, Jessica Placzek, Katie McMurran and Rob Speight. Additional support from Julie Caine, Paul Lancour, Suzie Racho, Ethan Lindsey and Patricia Yollin.