A 22-year-old visitor to Yosemite national park in California died after he was swept over a 594ft-high waterfall on Saturday, officials confirmed this week.

A fellow parkgoer, Freesia Gaul, was capturing a photo when she noticed the man, reportedly identified by local authorities as Josue Baires Alfaro, in the Merced River.

He did not appear to be a “strong swimmer”, Gaul told SFGate. A former volunteer lifeguard, Gaul jumped into the water in hopes of rescuing him.

“People see calm water, but they don’t realize that under that there’s a huge undercurrent,” she said.

“When you see someone like that, when you make direct eye contact with someone who you know is going to go over, you can’t turn around.”

In turbulent waters, Gaul could not reach Alfaro and struggled herself to stay afloat, SFGate reported. She thought her survival odds were bleak, until a bystander put forth a walking stick that she clung on to to avoid going over Nevada Fall.

The National Park Service has opened an investigation into Alfaro’s death, the Los Angeles Times reported.

Yosemite national park, located about three and a half hours east of San Francisco, is one of the most visited parks in America, attracting about 4 million visitors annually. It is a popular destination for hiking, water activities and cycling.

There have been several deadly accidents at the park.

In 2013, a 19-year-old from California died after swimming in the Merced River. He was swept downstream to Nevada Fall’s edge.

In 2018, an Israeli teenager died after plunging 800ft down a cliff while taking a selfie near Nevada Fall.

The National Park Service has warned parkgoers to use “extreme caution” near any flowing water or wet rock in that area.