Huffard first saw a coconut octopus running on two legs during a field trip in 2000 but only recently was able to capture the phenomenon on film. A paper on the subject was published last week in the journal Science.
When walking, these octopuses use their back arms like tank treads: A line of suckers is planted on the ground, and the octopus pulls itself forward.
Huffard clocked one coconut octopus traveling at approximately 2.5 feet per second and another moving at 5.5 feet per second going backward. That is slower than the animals can get through the water but faster than they can crawl.
Running, though, enables the octopuses to get away from a predator while remaining camouflaged, or at least not look like a typical fleeing octopus, according to Huffard and Full, who is a professor of integrative biology at UC Berkeley.
"This bipedal behavior allows them to get away and remain cryptic," Huffard said in a prepared statement. "This is the first underwater bipedal locomotion I know of."