Cryptonomicon

Wiley shifts up to high gear and floors it.

Flat grey clouds like shards of broken slate peek out between anvils.

Sometimes, if you want to live and breathe tomorrow, you have to dive into the black depths today, and that is a leap of faith—faith in your U-boat, and your crew—beside which the saints’ religious epiphanies amount to nothing.

"Well, it’s a truism that you can’t understand a person without knowing something about her family background, and so we have to do kind of a quick Cliff’s Notes number on the ancient Greek Theogony here.

He still had that relentless 24-Jam pressure in his head, but now his attitude had changed; instead of thinking of it as an anomalous condition easily remedied, it became his personal cross to bear, and really not all that bad compared to what some people had to suffer with.

"Compared to that, a little bit of sheet metal just was not very important to me. Of course, I know that a lot of guys would just stand back and allow someone they cared about to do something extremely foolish and damaging, only so that everyone concerned could then drive off to a miserable and emotionally fucked-up future in perfect, shiny cars."

He rolls out of bed, startling Rod, who (being some sort of jungle commando) is easily startled. "I’m going to fuck your cousin until the bed collapses into a pile of splinters," Waterhouse says.
Actually, what he says is "I’m going to church with you." But Waterhouse, the cryptologist, is engaging in a bit of secret code work here. He is using a newly invented code, which only he knows. It will be very dangerous if the code is ever broken, but this is impossible since there is only one copy, and it’s in Waterhouse’s head. Turing might be smart enough to break the code anyway, but he’s in England, and he’s on Waterhouse’s side, so he’d never tell

The chaos of the waves, gravid with encrypted data, mocks him.

The sand looks like a geometric plane until a sheet of ocean grazes it. Then small imperfections are betrayed by swirls in the water. Those swirls in turn carve the sand. The ocean is a Turing machine, the sand is its tape; the water reads the marks in the sand and sometimes erases them and some times carves new ones with tiny currents that are themselves a response to the marks.

Margaret really messes up his head. When it gets really intolerable, he goes to the latrine (so that the staff will not break in on him at an inopportune moment) and executes a Manual Override. But one thing he learned in Hawaii was that a Manual Override is unfortunately not the same as the real thing. The effect wears off too soon.
While he’s waiting for it to wear off, he gets a lot of solid math done.