...I'm momentarily transfixed, torn between curiosity and fear. I can pull it up the gently sloping mud bank, but then what? Already thought is lagging behind events, as the blotchy brown mass slides up wet mud toward me, its amorphous margins flowing into the craters left by retreating feet. In the center of the yard-wide disc is a raised turret where two eyes open and close, flashing black. And it's bellowing. A loud rhythmic sound that is at first inexplicable until I realize that those blinking eyes are its spiracles, now sucking in air instead of water, which it is pumping out via gill slits on its underside. And all the while it brandishes that blade, stabbing the air like a scorpion...