The deck moves beneath you, and it shouldn't. It really shouldn't—under just enough sail to keep steerage way, over a sea so nearly calm that the Bitch's own wake is the highest wave in sight—there is nothing which should rock her, be it ever so slightly, on her beam.
To starboard—nothing, nothing except the line still trailing over the rail as Quen winches it aboard, that and Lu making double time to haul it hand over hand lest the prize of the harpoon be lost.
To port, though—another line? No. Not a line at all. No line in the world ever had such dark and gleaming aspect under the moon and stars. No—the thing is back, back and reaching up over the rail of your fine ship to do—what? Surely it can't seek to do harm here, not after Emi saved its life. But—
No, it's left something on the deck, and it's pulling back that slender tentacle of itself. Pulling it back fast, as if afraid. Almost before you know what it is you're seeing, its tip whips up over the rail and disappears below.
But Emi saw it, too, and she leaps heedless up as if galvanized—far more quickly and strongly than you'd have credited possible, seeing how hard she drove herself at the capstan. On her feet in half a blink and chasing the thing—broad feet driving off the deck, sprinting as if she doesn't mean even to slow down at the rail—
—oh. She didn't mean to. By the time you're halfway to your feet, she's there, there and over the rail as if a hurdle, sailing over the side—no. Pulling off the rail, using it to snatch herself straight down overboard and at the water as if she meant to dive straight to the heart of the world that way.
There's a drill for this. You'd best start it, because you were the only one to see what the mad girl went and did—Quen's turn around the capstan has her back to you just now, and Lu's busy with the line just behind the starboard rail. To the bell, then—but salty as you are, the sheer strangeness of this moment has you rooted where you stand.
It's while you stand there, staring idiotically at the things the creature left—a sheath-knife and a fid? Why these?—that you realize you haven't heard the splash you should have. Even diving, Emi would've disturbed the water enough to hear, and it'd be strange if she were diving, since she can't even really swim—
—such are the thoughts which flee your mind in shock as you discover why you haven't heard a splash: there wasn't one. There wasn't one, because she is tangled in a mess of seaweed and somehow flying—