Hiker dies swimming in "extremely cold" lake just outside Yosemite

Thousand Island Lake, California
(Image credit: Getty)

A 19-year-old hiker died this week after taking a swim in an extremely cold lake. The young man was walking with a large group, including his father, in the Ansel Adams Wilderness.

At around midday, he decided to take a break and go for a swim alone. The teen was aiming to reach an island on Thousand Island Lake, but failed to return by 8pm, when his companions reported him missing. 

"Due to the urgent nature of the incident, a request was placed with the Governor’s Office of Emergency Services for a military helicopter to respond," said the Sherriff's Office. "Naval Air Station (NAS) Lemoore accepted the mission and responded to the location for medical assistance."

As The Mercury News reports, a member of the group called emergency services again shortly after saying that they had found the missing man, who needed emergency medical treatment. When emergency responders arrived, they found that he had died.

Cold shock

Police have not confirmed the man's cause of death, but have issued a warning that, even when summer temperatures exceed 100F on land, mountain lakes can still be extremely cold.

"At Thousand Island Lake, the overnight lows are in the low 40s at night, and the lake itself is fed by glaciers from Mount Ritter and Mount Banner," police said. "Even in the warmer months, the water is extremely cold."

As the National Weather Service explains, warm air temperatures can create a false sense of security, and cold water drains body heat much faster than cold air.

"When your body hits cold water, 'cold shock' can cause dramatic changes in breathing, heart rate and blood pressure," says the organization. "The sudden gasp and rapid breathing alone creates a greater risk of drowning even for confident swimmers in calm waters."

Cat Ellis

Cat is the editor of Advnture, She’s been a journalist for 15 years, and was fitness and wellbeing editor on TechRadar before joining the Advnture team in 2022. She’s a UK Athletics qualified run leader, and in her spare time enjoys nothing more than lacing up her shoes and hitting the roads and trails (the muddier, the better), usually wearing at least two sports watches.