Adithya Sambamurthy/The Bay Citizen

Lou Marcelli, a member of the Dolphin Club, swims in the bay on Monday, February 21, 2011. Marcelli, who is 83 years old, has been a regular Dolphin Club swimmer since 1943

On an overcast, blustery morning at Aquatic Park cove along San Francisco’s northern bay shoreline, the water temperature last week was a chilly 50.5 degrees. The air was only slightly warmer.

As they have been doing since 1877, members of the Dolphin Swimming and Boating Club plunged into the water. About a dozen swimmers, clad only in regular swimwear — no wet suits — did laps from their beachside clubhouse to the other side of the cove and back.

“This water is an attitude adjustment,” said Reuben Hechanova, the club’s president, calling the frigid surf “exhilarating.”

Now some of the club’s 1,200 members believe the city needs an attitude adjustment — and they intend to do exactly that by disrupting plans for the coming America’s Cup yacht races in 2012 and 2013.

Specifically, the swimmers object to a proposal to transform this tranquil cove into party central for the races, complete with a floating giant TV screen. The plan has received preliminary approval.

Evoking recent citizen uprisings on Wall Street and elsewhere, the Dolphins have named their protest Occupy the Bay.

“We don’t want them in the cove,” said Hal Offen, a club member and organizer of the protest. “We don’t want the big boats. We don’t want the Jumbotron.” According to event plans, the television screen would measure 44 feet by 22 feet and sit on a 140-feet-long barge.

While swimmers typically have broad access to the cove, during the months of the America’s Cup competition they are to be restricted to an area around the perimeter. Dolphin Club protesters say that if the city won’t change the plan, they will swim into the cove’s center, a busy area that would also include yachts affiliated with the races, and potentially cause havoc.

“Our real power here is to misbehave, to act up, to occupy,” said Offen, who equated the America’s Cup takeover of the cove as a classic example of the wealthy exerting power over ordinary citizens. “This is a rich person’s sport,” he said, referring to the cup races.

Jackie McEvoy, a club member, said of the yacht race participants: “They want us to see them as athletes. But they are making no effort to treat us as athletes. They’re treating us as a nuisance.”

Beyond hurt feelings or insinuations of class warfare, club members also have environmental concerns.

The video screen barge would most likely be powered by a generator, risking noise and air pollution and fuel spills. It would also need to be securely anchored to withstand winds.

Swimmers are worried that breaching the cove’s floor to secure the barge could dredge up toxins. According to the city’s 3,883-page America’s Cup Environmental Impact Report, the cove was a dumping ground for industrial waste in the 1800s, including material from a lead-processing plant.

In fact, it was the warmth from industrial pollution that first drew bathers to the cove.

“At least as early as the 1880s, bathers congregated in the cove to enjoy its warm waters — the result of heated industrial discharge from nearby facilities,” the report said.

The cove was later a dumping ground for debris from the 1906 earthquake.

But despite these historical accounts that seem to indicate that toxins are most likely buried beneath the cove’s floor, neither the Mayor’s Office of Economic and Workforce Development, which is managing the city’s role in the event, or the America’s Cup Event Authority, the organizer, could answer questions about whether poisons will be dredged up by the video barge’s anchors.

Stephanie Martin, chief communications officer for the authority, said that plans were still being formed and that additional details would emerge in January, “to work toward the best solution for all interested parties.”

Jane Sullivan, a spokeswoman for the city, said, “We’re hopeful we can work out the details to everyone’s satisfaction.”

For Walter Schneebeli, an 86-year-old Dolphin, the only option should be to leave the cove undisturbed. He has been swimming there since he was a child, and still does laps three days a week. In his long, intimate relationship with the bay, Schneebeli said he had never seen the waters so pristine as now.

“I’ve never seen them any cleaner,” he said.

With that at stake, along with 134 years of a hearty, eccentric tradition, it is no wonder the Dolphins are so defiant.

“Unless they have Navy Seals to arrest us,” said Andrew O’Mahony, 25, a club member, “we’re going to keep swimming.”

This article also appears in the Bay Area edition of The New York Times.