Athlete: Antarctic swim 'beautiful and harsh'
Endurance swimmer Lynne Cox
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(CNN) -- Lynne Cox, author of "Swimming to Antarctica," is an endurance and cold water swimmer. She has broken numerous records and was the first person to swim around the Cape of Good Hope, off the southern tip of Africa. Doctors have been studying Cox to determine how and why she's able to swim in frigid temperatures.
Below is an edited transcript of her interview with CNN.
CNN: Tell us a little bit about how you first became a swimmer.
COX: I think I first started swimming when I was in the bathtub at home. My parents taught my brother and sisters and me how to blow bubbles, breathe, move our arms and kick. When we were 1 or 2 years old we started swimming in the lakes of Maine, and off the beach in New Hampshire -- swimming in the ocean. That was my first exposure to the open water.
CNN: I would be interested to hear you just list the big swims you've done.
COX: I've done about 48 swims over the course of 30 years. And the first one was Catalina (Channel in Southern California), then the English Channel -- I broke the world record for men and women. I swam across Cook Strait. Swam around the Cape of Good Hope, first person to do that, Straits of Magellan. Bering Strait was real significant. That was one of the most political swims I did. The swims became a way to open borders and bridge distances between countries.
CNN: Your book that you have now is titled "Swimming to Antarctica." In a sense you started a long time before you jumped off the boat.
COX: The swim to Antarctica was basically a culmination of 30 years of long-distance swims and experiences. From knowing how to figure out tides, currents and weather patterns, to jumping into the water and knowing what kind of animals are there, and what you need to do for protection. Or what to look for in case your body is starting to go into hypothermia, or what to do if you're getting stung by stingrays, or jelly fish or any of the above.
CNN: How cold is the water down there?
COX: Where I did my test swim, initially in Antarctica, the water temperature was 33 degrees. My goal was just to swim for 10 minutes, and then to have the crew pull me out because we were concerned about my being able to have any kind of motor control at the end of the swim as far as hands feeling and pulling.
When I did that test swim I decided after 10 minutes I didn't want to be pulled out of the water. I didn't want to rehearse that, because being pulled out of the water is rehearsing to me failure.
CNN: What was the temperature when you did your final swim?
COX: The actual swim to Antarctica was in 32-degree water and the air temperature was 32 degrees, and the wind was about 30 knots.
CNN: What does it feel like to hit the water that cold?
COX: You feel an intense cold. In that first moment, your body is changing in huge ways. You're shunting the blood into the core of the body to protect the heart, lungs and brain. And so you are feeling that shift. Your blood pressure is changing instantly. You're hyperventilating. Your heart is beating very rapidly. You're trying to compensate and trying to create heat by moving your arms really fast.
I was really focusing on trying to keep my stroke rate so I could create heat. I also swam with my head up, because you lose up to 80 percent of heat through your head. I didn't want to do that the whole time -- because your efficiency goes way down. So I'd try to swim head up at least the first half. And then toward the end put my head down so I could be faster.
Lynne Cox enters the waters of La Jolla Cove in California.
The swim itself was extremely beautiful and harsh. Antarctica itself is an environment that is so beautiful. I mean everything is sort of reduced to the colors of blues, and whites, and greens. But also the harshness of it, that knowing that if you stay in the water a moment too long you can go into cardiac arrest.
CNN: What else was in the water with you?
COX: There were a lot of different animals in the water with me. There were seals and strapped penguins that slid down the glaciers and dove into the water and swam around me.
CNN: What's your training regimen?
COX: For swimming in Antarctica you have to go as fast as you can the entire way. So everyday that I trained I'd swim ... actually at first in my folks backyard pool where it would be 50 degrees in the winter time, I'd sprint for an hour head up, the entire time. And then when I went down to Argentina I trained in 40 degrees.
I was afraid I might have ear damage. My dentist suggested that we use dental material to make custom fitting earplugs. Then I was concerned about my teeth being very sensitive in the cold. And he explained that your teeth are porous. So he gave me three fluoride treatments to seal off the pores of teeth. I grew my hair longer to create an insulation level a little bit more under my cap.
CNN: What have you learned about why you are perhaps unique in your ability to withstand or work through cold?
COX: They've found that I'm able to constrict the blood flow to the peripheral area right away. I close down the skin, and put that in the core and keep the vital organs warm. And my body fat is very well distributed, so that sort of acts like an internal wet suit.