SAN FRANCISCO (KPIX 5) – For the second time in less than 24 hours, a swimmer in San Francisco Bay off Aquatic Park in San Francisco has been attacked by a sea lion.

The latest attack prompted Golden Gate National Recreation Area officials to close the park to swimmers until Monday.

SEA LION UPDATE @GoldenGateNPS is closing Aquatic Park to swimmers and will have more information forthcoming. Public Safety agencies working together on safety plan regarding sea lion. NPS is the lead agency at this time. @SF_emergency @SFPD @LondonBreed https://t.co/SdXisTK2Ts — San Francisco Fire (@sffdpio) December 15, 2017

According to witnesses, a man in his 60s was bitten as he was swimming around 8:00 a.m.

“A sea lion came up from underneath and grabbed him on the inside of his thigh,” eyewitness Andrew Burrell told KPIX 5.

A member of the South End Rowing Club was able to help the swimmer get back to shore.

“He came in shocked, he had a look in his face where he just wanted to get to the hospital,” Burrell said.

The victim was taken to Zuckerberg San Francisco General Hospital with three lacerations to his upper leg.

Friday morning’s incident follows another attack where a sea lion bit a swimmer in the arm off Aquatic Park around 2 p.m. on Thursday. In that attack, the swimmer was rescued by a sailboat and was also hospitalized.

Both victims are expected to recover.

It is unclear if the same sea lion in Friday’s attack was involved in Thursday’s incident.

Burrell, who said he has been swimming off Aquatic Park all week, questioned going into the water before the park was closed to swimmers.

“Out of 100 swimmers in the morning, I’m sure a lot of us will take a second thought on getting in the water, and I’m one of those,” he said.