SAN FRANCISCO — That bracing morning dip in San Francisco Bay lost a bit of its allure Friday after a swimmer was bitten by what was reported as a sea lion at Aquatic Park — the second attack by a marine mammal in less than 24 hours and the third in a week.
The bloody attack sent a chill through the plucky community of cold-water lovers and prompted the National Park Service to close the popular cove for swimming.
The injured swimmer, identified as Rick Mulvihill, suffered a “severe bite” around 8 a.m. and was being treated at San Francisco General Hospital, said Lt. Jonathan Baxter of the San Francisco Fire Department.
“It hit him right here, close to the family jewels,” said Bob Roper, 79, pointing to the inside of his upper thigh.
Roper and Mulvihill are both members of the South End Rowing Club, a 144-year-old group devoted to early morning bay swims.
On Thursday, another swimmer with the club was hospitalized in serious condition after being bitten in the arm by a sea lion, officials said.
The San Francisco Police Department’s Marine Unit pulled that swimmer out of the water around 2 p.m., according to authorities. Another member was bitten three or four days ago, but club officials said he didn’t require treatment.
“We are requesting that swimmers avoid Aquatic Park,” Baxter said.
The latest attack occurred as Mulvihill was swimming near the curved part of the breakwater pier, known to swimmers as “the Jacuzzi.” The creature apparently came up from underneath, bit him and swam off. He was pulled from the water by other swimmers who carried him to the street, where he was picked up by an ambulance.
“I’ve been here 50 years and I’ve never heard of anything like this,” Roper said. “You have a lot of very very nervous swimmers now and I don’t blame them. It’s pretty bad when you get bit by a seal. … It’s pretty serious. He was bit in the groin area and it was a pretty deep gash.”
Experts say the perpetrator could have also been a harbor seal, given that the two species are difficult to tell apart in the water.
Sea lions have long been a fixture along the northern waterfront. They are a popular tourist attraction at Pier 39. Their population swells during the winter. Swimmers say harbor seals are more common at Aquatic Park, but sea lions sometimes venture in after getting driven away by rivals at Pier 39.
Claire Simeone, a conservation medicine veterinarian at the Marine Mammal Center in the Marin Headlands, said it is not clear whether the culprit was a sea lion or harbor seal. Both species have been known to bite people in San Francisco Bay.
Simeone said she suspects the attacker was the same animal in each instance, but there is almost no way of determining that or figuring out why it has chosen to go on the offensive.
It is not pupping season — harbor seals breed from March through May and sea lions go to the Channel Islands from May through August to raise pups — so it probably isn’t a mother protecting her young, Simeone said. The most likely scenarios, she said, are that the animal is sick; young and curious; or it has been fed by humans and is now aggressively seeking food from them.
Such attacks aren’t unheard of. The Marine Mammal Center conducted a study of 10 pinniped bites in San Francisco Bay and one in Puget Sound, Wash., between 2011 and 2013.
The 2015 study, co-authored by the Dolphin Club and Sutter Health, did not find any identifiable pattern to the bites, except in one case the victim was trying to pet a harbor seal and another swimmer got between a seal and some bait that a fisherman had dumped.
Eight of the bites in the study occurred within a seven-day period in May 2013 and four of those happened at approximately the same time on the same day, May 15, 2013.
Bill Wygant, the president of the South End Rowing Club, said the rampaging harbor seal on that fateful day earned the nickname “Bitey.”
The latest attacks are similarly mysterious.
“Certainly it is concerning because its happened twice in 24 hours,” Simeone said. “We know that historically these bites are pretty infrequent.”
Curiously, Wygant said, most of the swimmers bitten during Bitey’s spree were members of the rival Dolphin Club.
“This time it has bitten three people from our club, but it’s early yet,” Wygant said. “From my experience this could go for several days, so we had to tell somebody. It’s all fun and games here until people start getting hurt.”
A sea lion attack can be very dangerous. The swimmer who was attacked Thursday had to have a tourniquet applied to his arm before he was transported to San Francisco General Hospital.
Simeone said sea lions and harbor seals are powerful wild animals. “They certainly have the strength to really harm somebody,” she said, “but the cases we saw in the study were all resolved without any long term consequences.”
But even a minor bite can be dangerous, said Tom Nuckton, a physician and Dolphin Club member who participated in the 2015 study. He said seals and sea lions have bacteria called mycoplasma in their mouths that can cause serious infections.
“It’s nasty,” Nuckton said. “You need the correct antibiotic.”
The fire department posted notices on Twitter and at the South End and Dolphin clubs announcing that the Golden Gate National Recreation Area was closing Aquatic Park to swimmers while public safety agencies worked “on a safety plan.”
That didn’t deter Lisa Serebin, 58, who ignored the hullabaloo and went on an hour-long swim Friday.
“It doesn’t bother me. I just stayed away from the area where they said they saw it,” Serebin said after climbing out of the water. “I’ve been bumped before, but it was no problem. Actually, I think about sharks more than sea lions.”