Below is a snippet of some tips from www.usatriathlon.org. I definitely have found that these help. In particular, the 2 caps, ear plugs, practice swimming in cold water and the blowing of bubbles. In addition, I do blow bubbles a bit aggressively as I start my swim. The bubbles blowing past the face seems to help the face adapt to the colder temps!
Here is a list of tips to minimize the negative effects and the uncomfortable feelings that can result from cold water swimming.
1. Wear two caps. You lose most of your heat through your head, and doubling up your “capage” helps you to keep your heat in.
2. Wear a neoprene cap. Neoprene is better suited for cold water than standard latex.
3. You also lose lots of heat through your feet. Neoprene socks are a good idea, but you may want to use these mostly on training swims, as they can be a hassle when it comes to transitioning to your bike on race day.
4. Wear a wetsuit—but more specifically, a full suit. The sleeveless suits allow heat to escape through your armpits. I learned this the hard way when doing the Alcatraz swim in 52 degree water with a sleeveless, Farmer John-style suit. By the time I finished, I was in the early stages of frostbite. Keep in mind that, according to USA Triathlon rules, wetsuits are allowed at triathlons with water temperatures of 75 degrees Fahrenheit or below.
5. Put in earplugs. When the water drops below 60 degrees, I think earplugs become necessary—and they do work well in keeping your core temperature up.
6. Practice swimming in cold water in the weeks before your race. At first, it can be a shock to your system that can lead to hyperventilating or a panicked feeling. You will want to swim slowly until you catch your breath. The first time you experience this it can throw you off, but with practice you will get used to it and be able to relax into your swim.
7. Do a significant warm-up the morning of your race (10 to 15 minutes, minimum). This will minimize the shock effect that cold water can have and allow you to get into a stroke rhythm much faster.
8. Blow bubbles before taking off on your swim. When the cold water hits your face, the shock causes your lungs to contract, causing breathing problems. Go waist deep into the water and submerge your face to blow bubbles. This helps alleviate the shock of the cold water.
Use these tips not only to help your body tolerate cold water swimming, but to use it to your advantage and gain a leg up on your competition.by