I had to look twice at this undersea Liberace-lookalike before recognising it as an octopus (more precisely, a blanket octopus, Tremoctopus sp.) These beautiful creatures live in the open ocean where they grow up to 2m long. The female in this image (thanks, Science Alert) has unfurled a sort of cape (called a 'web' in this Scientific American article) that may function in deterring potential predators - after all, you'd have to be fairly big to take on something of this apparent size. The web can be shed in sections, presumably acting as a distractor if the octopus is threatened by something large & hungry.
Interestingly, it's only the females who can put on this impressive display (the cape's rolled up when not in use), for the males are much smaller. So small, in fact, that it was some time before one of the 2.4cm males was even identified. That's a pretty extreme example of sexual dimorphism; in terms of the orders of magnitude between the size of the two sexes it must give some of the deep-sea angler fish a run for their money.
But also - it seems that small blanket octopuses (ie males & young females) use tentacles from Portuguese man-o-war jellyfish as defensive/offensive weapons, something that was first reported on back in 1963 (there's an image here on the ToLWeb site). Presumably these cephalopods are immune to the jellyfishes' stings.