"Closing in on what passes for the conning tower," Amy says. According to the book, this U-boat isn’t going to have the traditional high vertical tower rising out of its back: just a low streamlined bulge. Amy has piloted the ROV very close to the U-boat now, and once again she brings it to a stop and yaws it around. The hull pans into the screen, a variegated mountain of coral growths, completely unrecognizable as a man made object—until something dark enters the screen. It turns into a perfectly circular hole. An eel comes snaking out of it and snaps angrily at the camera for a moment, its teeth and gullet filling the screen. When it swims away, they can see a dome-shaped hatch cover hanging from its hinges next to the hole.