Octopus life is short and they mainly avoid other octopuses, as they are cannibal species.
I have seen octopus in specific area use broken glass to close her hole but still be able to see the predator. In short time in that area, many octopuses started using same technique, while short distance away not one of them knew this technique.
On Planka dive I have seen few times that octopus form a ball when cornered, usually they spit ink and try to escape through the fog. But for some reason these octopus make a ball and allow you to touch them.. Here is video I took.
Any way it is an interesting article in New York Times