Back Flip Into A Cold Pond

I have a story in one of my books of a young actress working with Katherine Hepburn and how she had to do a back flip into a cold pond for a movie scene. Hepburn was an avid year round ocean swimmer most of her life. She said to the young actress, you don't want to hire a stunt man, teach yourself how to do it! It will be rewarding and anyway you don't want to grow up to become soggy! This is how I feel about marching six miles dancing singing playing my bari sax in a parade. I wish to do this through my 80's and not become a soggy adult! I also would like to swim outdoors all year round. I have this physical endurance and skin temperature thing. I get high from exertion and I love the feel of cold water on my skin. It's fun!