Summarize this article in one sentence.
If a boat, dock, or some other solid object you can climb upon is no more than a few yards away, swim to it and get out of the water. Otherwise, stay put. Even strong swimmers can end up drowning when they try to swim in cold water. When too much body heat gets lost, hypothermia sets in very fast. Hopefully you're wearing a life jacket or personal flotation device (PFD), because it's imperative that you stay afloat. You don't want to have to do the doggie paddle to keep your head above water, since that uses up too much energy. Make sure your life jacket or PFD is fastened tightly, and lean back a bit to make it easier to keep your head above the water's surface.  Look around for something that may be floating in the water that could help you stay afloat. If your boat capsized, you may see a lifesaver ring, seat cushions, or other items you can grab. If you don't have anything to keep you afloat, you'll have to use your hands and feet. Try to move as little as possible, making only as many movements as necessary to keep your face out of the water. The Heat Escape Lessening Position, called HELP, keeps your body as warm as possible and conserves energy while you wait to be rescued. Draw your legs up to your chest and cross your feet. Wrap your arms around your chest and keep all your appendages close to your chest. Now "sit" in this position and bob on the water's surface.  HELP only works if you're wearing a PFD that keeps your head above the water without your having to move. Don't attempt HELP unless you're wearing a PFD. If you're wearing a life jacket that's designed in such a way as to make it difficult to assume HELP, assume the "survival position" instead. Keeping your head above the water, hold your body vertical with your arms straight at your sides, and your legs straightened and held together. If you're in the water with other people, the best way to stay warm is to huddle together. Get close to each other and lock arms and legs so that you're forming a big group hug. Make as much bodily contact with each other as you can. This uses up much-needed energy for survival. Have faith things will turn out if you are in need of rescue and keep as clear-headed as possible. As soon as you get out of the water, dry, off, warm up, and get  treated for hypothermia. If you were in the cold water for more than a minute or two, you could sustain organ damage, so it's essential that you get checked out as soon as possible.

Summary:
Swim only if a boat or solid object is in reach. Keep your head above the water. Assume the HELP position. Huddle if you can. Avoid panicking. Get medical attention.