Blue ring octopus are highly venomous to humans and there’s no anti-venom available.
I was impressed how the crab stands up on his back legs to fight. You want a piece of me dude? 
I didn’t know they could stand up.
This type of video fascinates me.
There was about 2 seconds of crab time, the rest of the time was just the oddly clumsy-looking octopus lurching around. Plus you have to disable your ad blocker. Not worth it, in my estimation.
Am I crazy, or is the text description of that video in the OP’s link pretty much total bullshit? (Not that those two options are mutually exclusive, of course.)
I watched the linked video, and none of that happened. The octopus went by one crab and smacked at it with a tentacle, and the crab sprang back into an upright defensive posture, and stayed there as the octopus moved on. Then the octopus encounters another crab which bats back its exploring tentacle and likewise jumps into defensive posture. Nobody jumped on the octopus’s back, no “epic” “locked in combat” situation occured.
In fact, nothing that I would call anything like a “battle” or “fight” or “combat” occurred at all. The octopus casually backhanded a couple of crabs in passing, like a bully walking down a high school corridor, and its victims smacked back once and retreated on the defensive. Nothing less “epic” could possibly be imagined, combat-wise.
As the article went on to say after it had gone through its clickbait-bullshit routine:
It was very cool to see the octopus and crabs going about their underwater business, but as a cataclysmic invertebrate battle on the sea floor this video is a complete washout. About what you’d expect from Mail Online.
The text is over the top hyperbole. That’s common these days with many news sites. I ignore it.
The video is only three minutes. The crab face off is short but with high stakes. The octopus venom can easily kill a crab. It was lucky to avoid a bite.
I read the daily mail with the duck duck go browser. It’s limited ad blocker doesn’t trigger any problems. I don’t get pop up ads with that browser. I do see a embedded ad when playing video.
When I read the thread title my first thought was “Is this some variation on Rock-Paper-Scissor”, like “Rock-Paper’Scissors - Lizard - Spock”?
Like “Octopus - Crab - Shark”, maybe.
Octopus beats crab, Shark beats octopus, Crab beats Shark?? Needs work.
What the video fails to mention: Afterward, the octopus ate the diver.
Well of course–she had already been seasoned.
I would also question if that was shot by a free diver, unless that water is very shallow. That’s a lot of bottom time. Not impossible, but at the limit for most everyone except world champion divers.
Definitely not a free diver, you can hear him breathing through his regulator throughout the video.