Since the start of winter quarter, scores of students have visited the newly-filled Lake Lagunita, with many running past the University’s cautionary signage on their way to the water. But what secrets lie beneath Lagunita’s murky waves?

According to Stanford ecology experts, debris, parasites, water-born pathogens and dead rodents may inhabit Lake Lagunita’s murky water, affirming previous warnings from the University advising students not to enter the lake. While the University only cautioned students against potential “debris, bacteria and deep mud,” experts said other contaminants may plague Lake Lagunita’s turbid waters. 

“There are undoubtedly many drowned rodents floating around,” said Alan Launer, the director of Stanford Conservation Planning. “When the reservoir suddenly fills, well, many of the resident rodents don’t make it and float around for a while until they decompose.”

“Me and my friends, we took a walk along the shore to count how many dead gophers there were,” said Daily staffer Steven Liu ’26. “We walked about 100 meters and there were 30 dead gophers.”

Along with decaying mammals, experts cautioned students that there may be sharp objects lying in the lake. “For decades people have left litter, including glass, at Lagunita,” Launer said. “As a result, there are quite a few items in the reservoir-bed which can cause large cuts.” 

Launer also spoke about “swimmer’s itch,” a skin rash caused by parasites in the water. Launer, who dealt with the rash for about a month in the 1990s, described it as “red lumps, which looked awful and were itchy.” 

Elena Litchman, an ecologist with the Department of Global Ecology, believes swimmer’s itch is a “real possibility.”

“Those parasites can swim underwater, and then they could basically enter human skin, burrow in it, and cause this allergic reaction,” Litchman said about the rash.

Luckily, recent cold temperatures may be protecting students from the parasite. “It’s all statistically possible, but at this low temperature it’s probably not that big of an issue,” Litchman said. However, she advise students to stay cautious. 

“Just in general, if it’s unfamiliar shallow water, you probably shouldn’t be swimming in it.” Litchman said. 

Alexandria Boehm, a Stanford professor of civil and environmental engineering, agreed with Litchman. 

According to Boehm, stormwater runoff often contains potentially dangerous pathogens, bacteria and eukaryotic organisms. “There’s a whole suite of different pathogens that are present in feces of animals and in sewage from humans that can end up in storm water,” Boehm said. 

“Swimming next to and in storm drains leads to higher risks of rashes, respiratory illness, and enteric illness like diarrhea and vomiting,” Boehm said. “There is the scientific observational basis for the advice not to swim in stormwater, for sure.”

While Boehm advises against entering the lake, she acknowledged some students may still take that chance. “Everyone has a certain risk threshold,” Boehm said. “So everyone decides what level of risk they’re willing to tolerate.” Many students will likely continue to enjoy the high water level before it slowly drains away.

“I wouldn’t swim in it, but I’d dip my feet in,” Hayden Kwan ’26 said. “I wouldn’t duck my head under the water.”

Some students appear more reluctant. 

“100% go to the lake to see the lake,” Liu said. “But don’t go into the lake, right?”