Part of San Francisco bay has been shut to swimmers following two rare attacks by sea lions.
A man was bitten in the groin area on Friday, a day after another man suffered a serious arm injury.
San Francisco’s Aquatic Park will be closed until Monday, the authorities said, suggesting that just one animal was responsible for the attacks.
Although unusual, the local Marine Mammal Center says there have been 10 such attacks over a three-year period.
San Francisco Maritime National Historical Park tweeted that the Aquatic Park would be shut following reports of an “aggressive marine mammal”.
The latest victim was taking an early morning dip when he was bitten on the upper thigh.
Another man, 56-year-old Christian Einfeldt, was bitten on the arm on Thursday while swimming in the afternoon.
“His head slid down my arm. Fortunately he only got one tooth into my arm,” said Mr Einfeldt.
It is not clear why the swimmers were attacked. Experts warn that sea lions can be erratic.
In May, a sea lion pulled a young girl into the water at Steveston Fisherman’s Wharf in Richmond, western Canada. She was unhurt.