While diving off the coast of Sulawesi, Indonesia, one diver captured video of a frogfish taking a stroll along the ocean floor. In the more than 1,000 dives that hobbyist diver Atsushi Sadaki claims to have been on, he says he's seen a few frogfish but never any moving in this way.
In the video, the frowny-faced fish can be seen hobbling forward on two front fins that splay out from the side of the animal's body. Frogfishes are "sit-and-wait" predators that pounce on unsuspecting smaller fish swimming past. Different species can be found throughout the world, but most tend to blend into their surroundings, meaning they don't really on speed or agility to find prey.
In an email with National Geographic, author of the book Frogfishes Around the World Ted Pietsch noted the frogfish in the video is likely a striated frogfish, which are commonly found throughout Indonesia but rarely seen thanks to their exceptional camouflage.
While the appendages may appear feet-like, they're actually fins. A 2012 study of the evolution of frogfish co-written by Pietsch and published in the journal Molecular Phylogenetics and Evolution noted that the fish accomplishes this type of locomotion by moving forward on pectoral fins and relying on the water's buoyancy to affectively bounce forward.
Before frogfish had been widely studied, it was believed they were amphibious and able to use this walking motion to move about on land. A 1734 study of the creature classified them as frogs, giving them the centuries-long misnomer.
However, the 2012 study found this to not be true writing, "A living frogfish removed from an aquarium and placed on a flat surface cuts a rather poor figure, its body more or less immobile and spreading out pancake-like under its own weight."
The study identified approximately 63 species existing in oceans around the world that have different methods of camouflage. Some have even been found to mimic sea sponges and urchins.
Frogfish aren't the only type of fish found "walking." In June, a diver also swimming off the coast of Indonesia filmed a stingfish performing a nimbler "walk" across the ocean floor. Unlike frogfish, stingfish have pectoral fins that are separated and more apt at movement. (Read why the video had experts stumped.)
Both stingfish and frogfish can be found in benthic zones, or the bottom of a body of water, where they lay in wait for prey.