A California teenager died after swimming out to an island in Thousand Island Lake.

The 19-year-old was hiking in the Ansel Adams Wilderness with his father and others when he decided to go for a swim around noon, by himself. After he didn’t return, the group contacted the Madera County Sheriff’s Office to report he was 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," the Sheriff’s Office said in a press release."Naval Air Station (NAS) Lemoore accepted the mission and responded to the location for medical assistance"

FLORIDA DRONE VIDEO CAPTURES SWIMMER FIGHTING OFF ALLIGATOR

Before the search and rescue team left, the hikers called the Sheriff’s Office to say they found the man and he needed immediate medical assistance, according to the release.

By the time the helicopter arrived at the scene, the man had died.

Police warned that swimming in alpine lakes is dangerous as they remain "extremely cold" despite high temperatures during the summer.

"At Thousand Island Lake, the overnight lows are in the low 40’s 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."

Police have not released the identity of the man or his official cause of death. 

Fox News Digital reached out to the Madera County Sheriff's Office for more information.