It's no secret that the Princess of Wales enjoys working out, but some exercises are too far for her husband, Prince William.

Appearing on Mike Tindall's podcast "The Good, the Bad, & The Rugby" with Princess Anne, Kate discussed the importance of staying active and revealed that one of her current fitness efforts is cold-weather swimming. The colder the better," she said. I love to swim. William says, 'Catherine, you're crazy. It's dark and it's raining.

According to People magazine, when meeting a close friend in Wales earlier this year, Kate talked about wearing a robe after swimming: "She said she wears a robe when she goes cold water swimming," said local Alison Cheek. According to an article in Harvard Public Health, cold-water swimming is thought to provide both mental health benefits and physical exercise benefits.

In addition to cold water swimming, Kate stays in shape by playing tennis and jumping on a trampoline with her three children before school.