SeeCalifornia.com

What happens when humans head into the Pacific Ocean on January 1 with temperatures ranging from 50 to 60 degrees? First, the cold water chills the skin, which has three to four times as many cold receptors as warm receptors. A sudden, strong urge to breathe and an inability to hold your breath combine to create hyperventilation, a sudden increase in heart rate and blood pressure. This response typically peaks about 30 seconds after you enter the water. In extreme situations muscles weaken and can cause a swimmer to become temporarily paralyzed. After the initial cold water touches your skin, it sinks down into nerves and muscle, potentially causing you to lose your ability to coordinate movements. Though the scenario seldom occurs, lifeguards are on duty at most Polar Plunges–New Year’s revelers are urged never to go into the ocean by yourself on Jan. 1.

Thousands of Californians and tourists will be going into the Pacific this New Year’s Day in an annual ritual that may be free or charges a fee for some special cause. Here is a list of plunge events.