Holy shit!!! Crab versus water pressure looks more like it. I watched it, and was totally unprepared for what I saw. So I looked at it again, and then a third time, wondering, "That's weird. Why did the crab not notice the rapidly-rotating blade it was about to stumble into?"
That was when I realized that it never touched the blade. It apparently thought it was safe, just wandering along past the blade, at a distance of an inch or two.
It was the water pressure across that tiny slit that got it. Holy shit.
What the fuck is that pipe made of? I'm extremely impressed.