Summary of article in Billed Bladet #25, 2017.
Written by Ulrik Ulriksen.
As you know Frederik attended the 60th anniversary of the Frogman Corps. He was himself a Frogman from 1995.
The Frogman Corps is under the navy, even though the command is directly under the Defense Command. And as you can tell from the photo with Frederik with his hands in the pockets, that is very much evident!
That is so typical of the navy. They are basically maritime hobos.
In contrast you'll never see anyone from the army with his hands in his pockets.
And there is a little but common misunderstanding in the article. Frederik's nick name was indeed Pingo, but not after this cartoon character:
Instead he was named after another penguin, named Pingu (in DK often translated to Pingo, just to confuse everybody).
He got the name after he went diving in a wet suit. Unfortunately the suits leaked and his legs ended up full of water, so when he got back on land, he couldn't walk properly, and with his flippers he walked just like this beloved penguin here: