Believe it or not, this is an octopus known as the blanket octopus. Aka the coolest cephalopod ever; I am not convinced that Superman isn’t based on one of these. When the female blanket octopus is threatened, she will release a thin, webbing “cape” that appears to increase her size and cause intimidation. I recommend this video (though it is not in English) if you want to see a blanket octopus in action.
Aside from their general appearance, there are a few really unique characteristics that these guys have which make them extremely interesting. First, they are completely immune to the venom of the Portuguese man o’ war. You know, those deadly creatures that resemble jellyfish (I’ll go into why they’re not actually jellyfish another time). The blanket octopus will actually carry man o’ war stingers around, using them to her own defense and to lure away potential predators.
You’re probably wondering why I keep referring to the blanket octopus as a female. Which leads to the second point of interest— the blanket octopus exhibits one of the highest degrees of sexual dimorphism in the animal kingdom (rivaled by many types of angler fish). This means that males and females look extremely different from each other. In the case of the blanket octopus, males are only a couple of centimeters long at most, and die immediately following reproduction.
Oh, and while I’m at it, the plural of octopus is actually octopodes. But octopuses is also acceptable— just not octopi.