Australian scientists filmed the veined octopuses selecting coconut shells from the sea floor, carrying them under their bodies up to 65 feet (20 meters), and assembling two shells together to make a spherical hiding spot.
Julian Finn and Mark Norman of Museum Victoria in Melbourne observed the activity off North Sulawesi and Bali in Indonesia between 1998 and 2008.
"Tools - something we think is very special about humans, exists in other animal groups that we've never considered before, a low life form, a relative of a snail. These octopuses, they're not simple animals," Norman said.
Their findings were published Tuesday in the journal Current Biology.