Chattan's position is the correct one. Detachment 2702 has a very clear and specialized mission which most certainly does not include opening safes from U-boats. For that matter, it does not include going onto abandoned U-boats to recover safes, or other crypto data, in the first place. The only reason they did that was because they happened to be the only people with Ultra clearance who were in the neighborhood, and U-553's precarious position did not give Bletchley Park time to send out its own experts.
But Waterhouse's desire to open the safe himself has nothing to do with Detachment 2702's mission, or his own personal duties, or even, particularly, with winning the war. It is something that Lawrence Pritchard Waterhouse is driven to do. His is not to reason why. Even as he was reeling down that stretched line from U-553 to the torpedo boat, battered by waves and wind and rain, with a busted arm and a busted head, not knowing from one moment to the next whether he would make it back to the boat or plunge into the Atlantic, he was remembering the infinitesimal tremors picked up by the half-frozen neurons in his fingertips as he twiddled the safe's submerged dial. Even as Enoch Root patched him up on board the boat, Waterhouse was constructing a crude mental model of how the safe's tumblers might be constructed, visualizing the thing in his mind's eye. And even as the rest of Detachment 2702 collapses into their cots and hammocks and sleeping bags around the chapel of Qwghlm Castle, the splinted and bandaged Waterhouse stalks the polished corridors of that building's better corner, looking for a couple of used razor blades and a hunk of carbon.
The razors he finds in a rubbish bin and the carbon he steals from the closet where Ghnxh keeps the galvanick lucipher. He brings them, plus a brick-sized crystal of hard glue and a blowtorch, back to the chapel, where everyone else is sleeping. Enlisted men are in the nave, as befits Marines who are basically a naval organization. Officers are in the transept: Chattan has the south arm of it all to himself, Waterhouse and Root and the SAS and USMC lieutenants have bunk beds in the north. A small moiety of Detachment 2702's astounding tarp supply has, then, been hung up across the eastern end of the place, partitioning off the chancel, Holy of Holies, where once the Body and Blood of Christ were housed. Now it contains a Hallicrafters Model S-27 15-tube superheterodyne radio receiver using state-of-the-art acorn tubes in its front end, capable of tuning VHF from 27 to 143 Megahertz and of receiving AM, FM, and CW, and including a signal strength meter which would come in handy if they were really operating a huffduff station here, which they aren't.
The lights are burning behind those tarps and one of the Marines is snoring away in a chair in front of the altar. Waterhouse wakes him up and sends him to bed. The Marine is ashamed; he knows he was supposed to be awake, twiddling that antenna convincingly.
The radio itself has hardly been used--they only turn it on when someone comes to visit who is not in on the Secret. It sits there on the altar, pristine, as if it had just come from the Hallicrafters factory in Chicago, Illinois. All of the altar's fancy bits (if it ever had them) have long since succumbed to fire, rot, plunder, or the gnawing tusks of nest-building skerries. What remains is a rectangular monolith of basalt, featureless except for some marks from the tools that were used to quarry and shape it. It is a perfect foundation for tonight's experiment.
Waterhouse gets the safe up there at some cost to the disks and ligaments in his lower back. It is tubular in shape, like an excerpt of naval gun barrel. He stands it up on its back end so that its round door, with the round dial in the center, is staring up at the ceiling like a blind eye, the radial lines on the dial looking very much like the striations of an iris.
Behind that dial is a bunch of mechanical stuff that has gotten Waterhouse completely pissed off, driven him into a frantic state. By manipulating this dial in some way, he should be able to tease that mechanical stuff into some configuration that allows the door to be opened. That's all there is to it. That this door remains locked is an outrage. Why should the tiny volume inside this safe--much less than a single cubic foot--be so different from the space that Waterhouse moves through at will? What the hell is inside there?
The glue looks like bad amber, flawed and bubbled but still beautiful. He fires up the little blowtorch and plays the flame over one end of it. The glue softens, melts, and drips onto the door of the safe, next to the dial, forming a little puddle about the size of a silver dollar.