The strange, rising shape has Jack's attention and he leans further over the edge to have a better view. His eyes widen when he sees it's a woman. Where did she come from? There's no nearby ship. He's ready to dive in after her when the truth of the situation starts to bubble up in his alcohol and exposure addled mind.
"Bugger me! Mermai.....aahhhh..."
He's over the edge and being hauled to the bottom before he can do anything to save himself. They're beautiful and terrifying creatures, all at once. When their mouths open and he sees their sharp teeth, Jack lets out a shout that travels to the surface in a large silent bubble and leaves him with even less air. He struggles in their grip and, once he has his wits somewhat about him, tries smiling sweetly at them for whatever good that might do.