Prince Harry joked about his crown jewels after he did a running jump into sub zero water in the Arctic.
After he took the plunge in a bright orange immersion suit the third-in-line to the throne said: "It's quite tight on the balls!"
The 26-year-old is in the final few days of training before he joins a group of wounded servicemen for the first five days of their trek to the North Pole.
The prince leapt bottom-first into an open stretch of water in the Arctic Ocean ice in his fully waterproof suit.
Moments before, he led the Walking With The Wounded charity co-founder, Ed Parker, to the edge and pushed him in.
Asked what it was like in the minus 1C salt water, the royal said it was a "silly question", then joked it was "warm".
When he first took the plunge, Prince Harry said: "It went up my nose."
He then said to Parker: "It had to be done."
Harry looked relaxed when he smiled and joked around as he wallowed in the icy water.
Simon Dalglish, the other co-founder of the charity, jumped on top of the prince, splashing the third-in-line to the throne across the face.
On Friday the prince will fly out to the start point of the 369km trek through the frozen wasteland.
The outside temperature today was minus 25C in Longyearbyen, on the Norwegian island of Spitsbergen, considered by polar experts to be the best place to train ahead of a trip to the magnetic North.
But the prince and his team mates will experience temperatures as cold as minus 45C on their trip.
They will need to put on the suits to cross cracks in the ice that could take hours to walk around.
But with howling winds, exhaustion and 100kgs of kit to haul, the task will be much more difficult than it was today.
Harry is patron of the Walking With The Wounded charity, which said it wants to raise STG2 million ($A3.11 million) from this unaided trek to help other injured servicemen and women find work, peace of mind and security.
