Kate Middleton's 'crazy' hobby - and she seeks it out everywhere she goes

The Princess of Wales has a number of sporty hobbies - but there is one activity she is especially passionate about, and her husband Prince William can't understand it

Princess Kate has picked up a 'crazy' new hobby - and she 'absolutely loves it'.

The sporty royal lives a very active life, alongside her husband Prince William and their three children. As a family, they love spending time together in the outdoors, whatever the weather - but one of Kate's favourite pastimes is a step too far for her husband.

In fact, Kate is so passionate about her daring hobby that she will even do it in the dark, as she revealed during an appearance on Mike Tindall's podcast, The Good, The Bad and The Rugby .

"I can always remember being physical, using our bodies, whether it's walking, climbing the lake district, in Scotland [or] swimming from a young age. [My parents] always encouraged us to be physically active and sporty and they always encouraged us into doing team sports and trying things."

She then shared her love of cold water swimming, which has many health benefits and involves swimming during the winter season in outdoor locations or unheated pools. Kate enthused: "Cold swimming - the colder, the better. I absolutely love it. Slightly to the point where William's [saying] 'You're crazy' and it's dark and it's raining. I will go and seek out cold water. I love it."

William and Kate are incredibly sporty and both have a serious competitive streak. During their appearance on the podcast alongside Princess Anne, Mike's mother-in-law, they were asked about their rivalry.

"I don't know where this has come from," Kate joked, before adding: "I don't think we've actually been able to finish a game of tennis. It becomes a mental challenge between the two of us," with William confirming the pair try to "out mental" each other for the victory.

When asked whether Prince George, Princess Charlotte, and Prince Louis were picking up this streak, Anne shared her thoughts, chiming in: "Just a little bit, I think." Kate then revealed: "They're all of different temperaments and as they're growing and trying out different sports, it's going to be interesting to see how that grows and develops."

William also spoke about the important life lesson he hopes to instil in his children through sport. "Learning to lose, which I think we've got to concentrate more on nowadays," he noted. "I think people don't know how to lose well. Talking about our children particularly, I want to make sure they understand that."

The Prince went on: "I think it's really important from a young age to understand how to lose, and why we lose, and to grow from it and what you learn from that process. But also to win well, and not boast. There's so many life lessons that help us all through life, in friendship building, in relationship building, workplace, that you gain from those early years of playing team sport."

William also revealed his most emotional sporting moment. "The only time I've ever cried when watching sport was when Zara won, I think, it was the European championship," he said. "I was down in Exmore at the time, camping. We were all huddling around the phone watching it. She was there, she was blubbing away, the flag was going up. I was in pieces." Kate added, "I can remember, because you came back and said ‘'I've never been so proud of anyone.'"