Now's not the best time to go for a swim, with elevated levels of bacteria swarming all over Ocean Beach.
The shoreline is always a bit of a petri dish, but heavy rains have forced the city to dump dirty sewage into the ocean and bay. It's a regular practice that happens about a dozen times every year whenever the wastewater system is overwhelmed by rain.
The discharges happened last Thursday during the worst of the rain, according to the Ocean Beach Bulletin.
Discharged water has been treated, but only slightly. It's gone through a system of boxes and channels that help to screen out the largest debris, but harmful chemicals and organisms remain.
In response to the pollution, the city posted closure notices at Ocean Beach, Mission Creek Channel, and near Candlestick Park.
Since Thursday, the water has cleaned up a bit, and the beaches have been re-opened for use. Water quality along the northern edge of the city is likely the cleanest, since fast-moving currents in and out of the bay help to dilute discharges.
But several stretches near the wastewater treatment plant are not regularly tested, so swim at your own risk.