On Memorial Day Weekend, Lisa Ludwigsen went for an afternoon dip at Chicken Ranch Beach. A regular swimmer in the bay for two decades, she and a friend swam offshore as the tide ebbed to its lowest point. The water felt warm—no need for a wetsuit—but was cloudy and opaque. She treaded as they discussed where to swim next. That’s when she felt the bite.
“Something came up and clearly bit me. It felt like…