Kate took the plunge at Cathedral Quarry in Little Langdale, Cumbria after having a go at mountain biking with a group of Air Cadets on Tuesday.
Thirteen-year-old Itelouwa Odipe, from Lancaster spoke to the duchess, who is Honorary Air Commandant of the Royal Air Force Air Cadets, as she waited to try abseiling.
He said: “She was about to abseil and I was next in line so she asked me if I wanted to go before her. I was a bit scared so I said no.
“She said if I did she would meet me down there.”
The teenager spoke to her again after deciding not to brave the drop.
“She said it was really good and I should try it,” he said.
“I think she was very kind. Even though she is a royal highness she still does things normal humans do.”
Looking forward to a day spent outdoors in this beautiful landscape! https://t.co/wsahE7e86t
— The Duke and Duchess of Cambridge (@The Duke and Duchess of Cambridge)
The duchess asked the teenagers about the activities they took part in and how the pandemic had affected their mental health.
She said of the activities: “It’s so great to have these challenges.”
Josh Binnie, 15, from the Kendal squadron of the cadets, told her about his experience in a glider and was asked by the duchess whether it made him travel sick.
When he said no, she replied: “You’re made of tougher stuff than me.”
Josh said: “She was very nice, a lot less formal than I expected.”
Fergus Ripley, 16, from Lancaster, said: “It was a fantastic experience to talk to Her Royal Highness.
“It was great to see her get involved.”
The cadets also made a cup of tea for the duchess, who wore black jeans and a green coat with brown boots.
Abby Armstrong, 14, from Lancaster, said: “I found out this morning we would be meeting her and it was a total shock. I was just like ‘wow’.
“She was very nice and not what I was expecting, she was more down to earth.”
The duchess also spoke to former cadet Emma Wolstenholme, 39, who is planning to row across the Atlantic to raise funds for the organisation in its 80th anniversary year.
Ms Wolstenholme said: “She thinks it’s incredible, an amazing challenge.
“It’s such a great cause. I joined the cadets at 13 and went from being the quietest kid in the school to one of the more confident, outdoorsy and adventurous ones.”
The visit marked the reopening of the Windermere Adventure Training Centre following a £2 million refit.
The centre will allow hundreds of cadets from across the UK to visit the Lake District each year and take part in a wide variety of activities, building their confidence and leadership skills and achieving their Duke of Edinburgh Awards.
After spending time with the cadets, Kate was due to go on a boat trip with with two of the “Windermere Children”, a group of 300 child Holocaust survivors who came to stay in the Lake District in 1945.
She will also meet relatives of survivors to talk about how their loved ones’ time in Cumbria helped them to go on to build successful lives in the UK.