Fishing Highlight of the Week: You should always wear your life jacket, but when water temperatures are less than 40 degrees, it's even more critical. When a person falls into water that cold, the body's automatic reflex is to suck in air. If your head is under water when this happens, you'll pull in water as well. Without a life vest keeping you above water, coughing up that water is extremely challenging. Even great swimmers can drown in winter weather if they fall overboard.