It has been reported that octopuses can also travel by bi-pedal walking. Walking on two arms (or legs, if you will) is a slower more inconspicuous means of movements for the octopus. Both crawling and bi-pedal walking are safe modes of travel when there are predators nearby; crawling or walking allows the octopus to quickly escape a predator's clutches without drawing attention to itself. Often, when octopuses crawl or walk, they look like plants!
The movement that octopuses are often marveled at for is swimming by jet propulsion. This is the octopuses fastest means of locomotion. This process takes place by the octopus drawing water into a cavity in its body, then expelling the jet of water from a contractile mantle, and aiming it via a muscular siphon. The force of this squirting is so powerful that it moves the octopus swiftly backwards through the water. That is why octopuses swim headfirst, with their arms trailing behind.