It's a tale of perfect camaraderie and of co-dependence.
Two years at sea have fostered a close relationship between the two fellow sailors as they cross the globe, through warm weather and cold.
One is a 24-year-old male. The other is a hen.
Guirec Soudee - the 24-year-old - is the one who does most of the hard work on board the boat.
Monique is the hen, who spends most of her time admiring the view from the deck, and laying the occasional egg.
(All images are courtesy of Guirec Soudee)
The two have started building up a close following online in recent months as French media have picked up on their unusual adventure.
Guirec, who is from Brittany in France, began his trip around the world with Monique in May 2014.
After starting from the Canary Islands, Spanish territory near Africa's west coast, the pair sailed to St Bart's in the Caribbean before moving into the Arctic last August.
"I knew she was the one straight away," Guirec tells the BBC from western Greenland, where he is now moored.
"She was only about four or five months old then, and had never left the Canary Islands. I didn't speak any Spanish and she didn't speak any French, but we got along."
Guirec had planned to bring along a pet for company, but a hen wasn't originally on the cards.
"I thought about a cat, but decided it would be too much effort to look after it," he says.
"The hen was an ideal choice. It doesn't need that much looking after and I'm able to get eggs at sea. People told me it wouldn't work, that the hen would be too stressed and wouldn't lay eggs.
"But there was no problem, she laid eggs straight away. She adapted to it perfectly - she was very comfortable very quickly."
Over an average week, Monique lays six eggs, even in the cold climes of Greenland and even during three months there without sun.
Guirec says locals in Greenland have reacted with some curiosity to her presence - understandable, perhaps, given there is no poultry farming there.
Life is pretty comfortable for Monique on board the 11.8-metre (39ft) boat, named Yvinec after the island on which Guirec grew up.
While she is free to roam the deck most of the time while at sea, Guirec makes sure to put her back into her hutch when the weather worsens.
"At the beginning, I was very worried - there would be huge waves and she might stumble, it would look for a second like she might go overboard, but she would always regain her footing. She's very brave.
"But when there are bad winds now, I'm much more careful and she goes inside."
One thing Guirec may also have to be careful about is quarantine regulations. While his and Monique's friendship survived its only encounter so far with customs officials, in Canada, he acknowledges it may not be so easy next time.
Not that Guirec is apprehensive about the prospect of their relationship being broken up. "I'm not too worried about that," he says. "I'm a positive person."
There are positives to be taken, too, from having a hen instead of another person on board. "Compared with people, she doesn't complain at all.
"She follows me everywhere, and doesn't create any problems. All I need to do is shout 'Monique!' and she will come to me, sit on me, give me company. She is amazing.
"But I won't lie, she can get on my nerves sometimes."
So what do Guirec's family and friends make of his choice of seafaring companion?
"They found it very funny," he says. "They've always known I'm not totally normal, anyway."
The next part of the trip will take the pair through the Arctic and down the Bering Strait towards Nome in Alaska.
And from there?
"We're not sure yet," Guirec says. "We haven't talked about it yet, but we will.
"We talk a lot, Monique and I."