Dumbo octopuses move by slowly flapping their ear-like fins, and they use their arms to steer. They are foraging predators and eat pelagic invertebrates that swim above the sea floor. As there are few large predators in the deep sea, dumbo octopuses’ primary predators are diving fishes and marine mammals, including tunas, sharks, and dolphins. Due to their preference for extreme depths, they are only very rarely captured in fishing nets.
Source: http://oceana.org/marine-life/cephalopods-crustaceans-other-shellfish/dumbo-octopuses