An octopus does have eight legs, hence the OCTO (eight) in the name. Squid have eight arms/legs too, but two additional tentacles that don’t function as legs. A thing with six legs that lives in the sea...I don’t know what it would be. Scientists found an octopus that’s missing two of its own legs due to a birth defect. So octopus might technically be right, if they are referring to the animal named “hexapus”