Rescue workers are still searching for a 19-year-old Sacramento man who is believed to have fallen over the edge of a waterfall at Yosemite National Park on Sunday. The man, Aleh Kalman, is now presumed dead.

"We believe a fall from the top of that waterfall is not survivable," park spokeswoman Kari Cobb said. "We have moved to limited, continuous searching."

The Nevada Fall is almost 600 feet high and is fed by the Merced River. The river usually sports sub-60 degree temperatures and swiftly moving waters, a recipe for disaster should someone get swept away.

That's exactly what happened to Kalman. He was swimming upriver about 150 feet away from the waterfall. Eventually the current picked up and he was unable to swim back to shore. There are currently no park rules against swimming in the river despite the clear risk of doing so.

"It's almost impossible to survive," Yosemite National Park ranger Scott Gediman said. "We don't recommend swimming in that river anywhere, we would assume that people who choose to swim in those areas know that if you go down, you're going to go over the side of the fall."

Kalman was at the park with a group from the Second Slavic Baptist Church in North Highlands, which serves churchgoers who hail from Russia and other Soviet satellites states. Despite the odds, his friends and family are still holding out hope for his safe return.

"All we can do right now is pray, just hope for the best. It's all in God's hands right now," his friend Bogdan Pishtoy told KOVR-TV.

There have been multiple deaths due to the waterfalls in Yosemite. Most recently, Kenneth Stensby was found dead at the base of Vernal Fall last month. Officials have closed the trail under Nevada Fall while they continue looking for the body of Kalman.