MILWAUKIE, Ore. (KOIN) — A kayaker is believed to have drowned on the Willamette River in Milwaukie, deputies said Thursday.

Witnesses called 911 around 4:30 p.m. to report a man had fallen in the water after his kayak flipped near Elk Rock, the Clackamas County Sheriff’s Office said. He was not wearing a life jacket.

Deputies said several people went out to help the man but he disappeared beneath the surface before they could reach him.

This is a dangerous time to be on the water, authorities say, as temperatures in rivers are deceptively cold. 

“We’re still early on in the season so we’ve got warm temperatures—ambient air temperatures—but the water is still cold,” said Brandon Paxton with Clackamas Fire District #1. “So that causes problems every year for folks who are surprised to get in the water and their bodies just don’t perform as well as if the water was a little bit warmer.”

The man who fell into the water has not been identified. 

Several agencies responded to help find the man, including the Coast Guard, the Multnomah County Sheriff’s Office and various dive teams.

KOIN 6 News will update this story as soon as possible.