Florida's coastline is a veritable goldmine for conchologists eager to add interesting seashells to their collections, but newbie "shellers" should remember Rule One: before making off with your bounty, always check there's nothing living inside …

Footage recently captured on a beach in Florida's Pinellas County shows us just why that's important. Uploaded to the Friends of Fort DeSoto Park Facebook page, the clip features a small octopus seeking refuge in a shell after washing up on the beach at the end of last year.

Although Floridians are used to seeing all manner of crabs and mollusks wandering around on their beaches, octopuses are a little rarer. According to Monica Craig, a member of the Friends of Fort DeSoto Park who filmed the eight-armed beachgoer, a recent cold snap may have contributed to the unusual wash-up.

"With cold fronts also come unusually high and low tides, which means the animals get washed further up the beach and are less likely to be able to get back down to the water's edge," she explains. "When the water gets significantly colder than normal it is also common to find many species cold-stunned on the beach, also having been washed up during high tides and left when the tide goes back out."

Once the animal had squeezed itself into the shell, Craig returned it to the safety of the water. 

The cephalopod was most likely an Atlantic pygmy octopus (Octopus joubini). "They commonly inhabit empty shells for shelter that they find on the open sea floor," explains Eric Hovland, Associate Curator at The Florida Aquarium. "The storm could certainly have raised it from the sea floor and deposited it on the beach as it was discovered," he adds. The species is common in the Tropical Western Atlantic, and like other octopuses, it prefers spending its time on sheltered areas of the ocean floor, where it's easy to put those colour-changing camouflage skills to good use..

Unlike other mollusks such as clams, octopuses lack a protective exoskeleton, so they'll often use their impressive shape-shifting skills to squeeze into a shell or rock crevice to evade predators. Some species, like the coconut octopus (Amphioctopus marginatus), even haul their body armour around with them so they can easily duck for cover when threatened.

Of course, hiding out in a shell can backfire if your protective carapace gets hauled off by humans, which is why Craig warns against removing anything from the beach without checking for marine life first (under Florida Fish and Wildlife rules, removal of any seashell containing a living organism is illegal unless you have a licence). Better still, leave beach treasures where you found them – research suggests our love of shell collecting damages aquatic ecosystems. 

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Header image: Kevin Bryant

Editor's Note: A previous version of this article misidentified the species as a common octopus. This has been amended.