The 29-year-old, who's on a 300 km (186-mile) trek across Antarctica in support of the Walking with the Wounded charity, called the four members of the Row2Recovery team ahead of their 3000-mile race across the Atlantic. (See the video below.)
All bundled up against the freezing temperatures and sitting on a camp bed inside a tent, the prince joked with the soldiers, who were standing in the sunshine in the Canary Islands. "It's minus 30 [Celsius] here, apparently it's plus 30 where you are," he said.
After skipper James Kayll said that it was even warmer than that, Harry rubbed his unshaven face and admitted that they'd had a few setbacks prepping for their frigid walk but were ready to set off.
Kayll told him that they were starting on Monday, but as he pointed out that rowing 3000 miles was "a little bit further than your walk," Harry made a face.
"Rowing 3000 miles is a hell of a lot easier than walking 300 kilometers, by the way," Harry joked.
The prince ended the conversation by wishing the rowers good luck and jokingly warning them to "avoid the occasional great white shark coming underneath the boat."