Visitors to Yosemite National Park are being told to stay away from the water.
The Merced River is at flood stage and rescue personnel are training for what could be a deadly summer.
The snowmelt in the high Sierra means Yosemite's waterfalls are spectacular, but the Merced River running through Yosemite Valley is running high and posing a hazard.
"It's cold melted snow and we are getting the word out to visitors to keep your distance from the water," says ranger Scott Gedimen.
Unless you are a member of the Yosemite Search and Rescue team.
They are braving the cold rough water to train in how to save the life of someone in the water. But that someone is most likely to be a fellow rescuer, not a visitor who falls in.
"The reality of work-based events is it's recovery, not rescue. Two-thirds of the missions I've been on historically are body recoveries," says Moose Mutlow of Yosemite Search and Rescue.
On a hot day, the water might look inviting, but it's freezing, actually about 46 degrees. You may not make it out if you fall in.
There have been 22 drownings in the river in the past 10 years, and there are more than 200 various search and rescue operations in the park every year, including stranded climbers, injured hikers.
There is so much to see and do in Yosemite, drawing millions of visitors from around the world every year.
Rangers and rescuers just advise everyone to be careful and for at least the next few weeks, stay away from the water.