A day out on Lake Washington is so picturesque, you'd think the beauty could take your breath away, but deputies with the King County Sheriff’s Marine Unit worry there’s something else most people aren't prepared for that really puts them in danger.

River and lake temperatures are so frigid right now, cold water shock is a big concern.

Deputy Ben Callahan likened it to the sensation you feel when you stick your hand in a bin of ice water.

"This feeling causes your diaphragm to react and causes your muscles to seize up,” he explained.

Callahan said Lake Washington might be close to 66 around the surface, but just a few feet below, it drops dramatically. And if somebody suddenly falls in, they can suck water into their lungs.

Deputies say the temperatures in local rivers are even colder. For now, they're warning people just to keep out.

"That water is snow runoff, it is cold and it will kill you," said Callahan.

They will be patrolling Lake Washington and Lake Sammamish throughout the weekend and into the early morning hours. They can write tickets, but mostly issued verbal warnings and encouraged people to review boater safety guidelines.