Beachgoers in Hawaii managed to re-float a paper nautilus after it stranded in Oahu this week. Exactly what brought the animal inland is anyone's guess, but local marine biologists suspect it recovered from its misadventure. 

Despite what its common name would have you believe, this creature is not actually a nautilus. In fact, paper nautiluses are only distantly related to the shelled molluscs they share a moniker with. What you're looking at is one of the world's weirdest octopuses, an animal more formally known as an argonaut. 

Few people in the world study these oceanic oddities because they tend to stay far offshore and out of sight.

"I don't think that they come in close to shore very often," University of Hawaii marine biologist Megan Porter explained in an interview with local KHON2 News. "Or they're out at times when people aren't in the water. To have one wash up on shore where people can actually see it, it's actually quite rare."

Male argonauts measure in at just a centimetre in length, and also lack the enlarged tentacles used to secrete calcium carbonate shells. That means the Oahu find is most definitely a female. 

Back in 2015, divers in California encountered a gaggle of female argonauts swimming together. We checked in with Museum Victoria's Dr Julian Finn, one of the world's leading argonaut experts, and he'd never seen anything like it. 

There's a lot about the lives of these strange animals that we still don't know, but along with his colleagues, Finn discovered that those delicate shells help to keep female argonauts afloat as they move through the water column. 

"In the early days people didn't really understand what was going on," he told us. "They would find an octopus within this shell, and these long webs. A mythical story began around the time of Aristotle that says the argonaut female actually lived in the shell and raised those webs as sails, to sail across the oceans."

In reality, the shell – which is about twice the thickness of a human hair – acts more like a ballast than a sail. The argonaut "gulps" air at the surface, which is then pushed into the shell to maintain buoyancy underwater. As you can see, shell-toting argonauts aren't particularly strong swimmers. Porter speculates that this one was simply pushed to shore by a large swell, or that light pollution drew it off course.

And it's likely that this female had more than just a bubble on board. Argonauts also use their thin shells as makeshift cribs to protect brooding eggs. Here's hoping she went on to swim another day!

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Top header image: Ewald Rübsamen - Die Cephalopoden/Wikimedia Commons