The grid’s woven from pencil-thick rods spaced a couple of inches apart. He’s facedown on it, looking into a hold that, if this U-boat were level, would be below him. The hold is a disaster, its neatly stacked and crated contents now Osterized into a slumgullion of shattered glass, splintered wood, foodstuffs, high explosives, and strategic minerals, all mingled with seawater so that it sloshes back and forth with the rocking of the dead U-boat. A perfect, quivering globe of silver falls through the grating right near his head and descends through his flashlight beam and explodes against a piece of debris. Then another. He looks uphill and sees a rain of silver globules bouncing and rolling down the deckplates toward him: the mercury columns that they use to measure pressure must have been ruptured. There’s another blinding blue flash: an electrical spark with a lot of power behind it. Shaftoe looks down through the grid again and perceives that the hold is filled with huge metal cabinets with giant bolts sticking out of them. Every so often a piece of wet debris will bridge the gap between a couple of those bolts and a spark will light the place up: the cabinets are batteries, they are what enable the U-boat to run underwater.