Gabriel Jabbour couldn’t help but shake his head as he eased his boat past sunburned throngs guzzling cans of spiked seltzer in the packed waters of Cruiser’s Cove last weekend.

The cove next to Big Island has long been summer party central for Lake Minnetonka boaters. But some longtimers like Jabbour say that nowadays, booze and loud music are the least of their worries.

Last month, a mysterious outbreak sickened 116 people who had been in the water during the July 4 weekend — the Super Bowl of lakeside debauchery. The news alarmed surrounding residents and many who come to the lake to party or for a refreshing swim.

“If anybody tells you the geese did it, I have never in my life seen geese out here,” said Jabbour, owner of three area marinas and the self-styled “Mayor of Big Island.” More likely, he says, is that one of the boats dumped its sewage while anchored, rather than heading back to a marina and taking the risk of losing its spot in the mob of vessels.

His solution is a simple one: Team up with the Hennepin County Sheriff’s Office Water Patrol to search for boats with built-in toilet pumps, which he argued have no place on a lake with so many pumping stations. So far, he says, local conservation officials aren’t listening.

Making another pass around the cove, Jabbour pointed to the “family” area, where a half-dozen boats bobbed lazily in the waist-deep water. “And this,” he said, jabbing a finger farther west, “is where the party animals are.”

And any potential risk of getting sick was not keeping them out of the water last weekend.

Standing on a boat drifting through the “party” zone, Makayla Dreier watched as other members of a bachelorette party she was with, including the bride-to-be, splashed around nearby. She had seen the headlines about elevated E. coli levels, but said that that wasn’t going to stop her from joining the fun.

“I was obviously concerned, but one of the girls brought hand sanitizer,” said Dreier, 22, who drove up for the day from Norwood Young America.

A few yards away, a man who had been coming to Big Island for 22 years said that he didn’t think twice about getting in the water.

“Obviously, if you drink the water, you don’t know” what’s going to happen, he said. “Long story short, you’ve gotta use common sense.”

Some lake users fret about what they see as a lack of responsiveness by the Lake Minnetonka Conservation District, which regulates use of the waterway.

Jake Walesch, a Deephaven resident who is on the board of the LMCD, said he would push for a public education campaign because people “don’t understand the mechanics of the pumps or they aren’t aware of what’s happening.”

“There’s no reason to have the pump on there if you’re not planning on pumping it in the lake,” he said. “It’s dangerous and disgusting and should be common sense, but apparently it’s not.”

Hennepin County Sheriff’s Office spokesman Edgar Linares said the department would gladly help health officials if they asked to use their boats, “But the thing is we can’t stop people from going in the water.”

“It’s not really our thing; we’re not taking a lead on this,” he said.

Tracking the outbreak

The July 4 outbreak came as high levels of E. coli forced the temporary closure of 11 Twin Cities beaches. The number of closures peaked at 49 and 45 in 2015 and 2016, respectively, when summer rainfalls were heavier than average. But unlike most of those cases, caused by rain runoff tainted with animal feces and other contaminants, officials say the Big Island health scare was caused by humans.

Jabbour’s theory, shared by others, is that it was the work of a single boat that illegally dumped its sewage. Another possibility, health experts said, was that a single person with norovirus defecated or vomited in the water, exposing hundreds of nearby partyers to waterborne illnesses.

Investigators may never get an answer, said Trisha Robinson, supervisor of the state Department of Health’s waterborne diseases unit.

MDH uses predictive modeling to close beaches based on temperatures, currents and other indicators of bacterial contamination. Still, further testing may provide important lessons for preventing another outbreak, she said.

“The congregated area that is Big Island is like a big bathtub, so that if you are in the water, you are sharing the water,” said Robinson.

One test for norovirus turned out negative. Robinson said people need not worry about swimming in Lake Minnetonka, or any other lake for that matter, but urged them to observe beach closures and exercise normal precautions, such as rinsing off before entering the beach to avoid contaminating the water.

In the past, conservation district officials have discussed several solutions to lake contamination, such as imposing stiffer fines, adding civil penalties, installing a camera at Big Island, putting up a floating latrine or limiting the number of boats around the island.

On the recent afternoon, Jabbour’s boat darted past orange, white and blue buoys, marking lanes for emergency personnel to ensure there will be no repeat of 2003, when boaters blocked rescuers from getting to an intoxicated man who fell overboard and later died.

Back at the cove, high-tempo music pumped from a growing gaggle of boats, as partyers drank, danced and posed for selfies. Some took off their shirts and basked in the midday sun, while others tossed a football in the water.

By 2 p.m., nearly 100 boats dotted the water. On some weekends, they can number between 400 and 500, locals say.

Jabbour says he’s learned to tolerate the crowds. And while he says that most show respect for the lake, some don’t.

Twice a week, he and a small army of volunteers head to the island to collect litter and empty beer bottles, left behind, he believes, by underage drinkers who are reluctant to bring any incriminating materials home with them.

“We’re trying to leave it the way the glacier left it,” he said.

As Jabbour’s boat drifted closer to shore, Terry Deggendorf and her brother, Tom, strolled down their dock to greet Jabbour.

Terry Deggendorf, whose grandparents built the family’s cabin on the island in the 1940s, also suspects that someone dumped their waste into the water.

“These people are out here eight hours, 10 hours a day, and some of these boats don’t have bathrooms,” said Deggendorf, who lives in Coon Rapids.

As she spoke, Noah Waterhouse clung to the side of the boat, which rocked gently in a light breeze. He calls it the “Fourth of July paradigm”: Every year, first-time visitors get so caught up in alcohol-induced euphoria that they forget their manners, he says.

“It’s not truly lake people,” said Waterhouse, a regular visitor from St. Bonifacius, who joked that he himself “moved down to the family side from the wild side” after the birth of his first child.

Balancing on an inflatable float, Christine Myers said that her first memory of the lake was learning to water ski at the age of 6. In her mind, anyone who grew up on or around the lake respects it too much to dirty its waters.

“Not everyone is out here to party,” said the Watertown resident. “We would never do that: We care about this lake.”