How has Gene's wave metaphor from chapter 8 intensified?

In chapter eight, the romanticizing Gene writes:

So the war swept over like a wave at the seashore, gathering power and size as it bore on us, overwhelming in its rush, seemingly inescapable . . .

Except that, as he goes on to say, Finny makes the war bearable by denying its reality. This allows Gene to "duck" so that the wave that is World War II passes overhead, leaving him "peaceably treading water."
Of course, even in the privileged environs of a wealthy prep school like Devon, war intrudes. Leper goes to war full of romantic visions of being an Alpine fighter on skis in a pure, snowy landscape, and then he goes AWOL because the reality of war causes him a nervous breakdown.
The parallel "war" Gene has been fighting internally over his desire to come clean to Finny about shaking the tree also comes to a head and crashes down like a wave on both boys (though at this point Knowles doesn't use that metaphor) when Brinker stages his mock trial. It reaches crescendo as Phineas tries to escape the "wave" of having to acknowledge Gene did shake the tree and cause his fall.

The question is unclear as to how far past Chapter 8 it is asking about, so it is difficult to say exactly how Gene's situation has intensified. In Chapter 8, Gene describes the war as a "wave at the seashore." It's powerful and ominous; however, Gene is able to duck it and avoid all of its danger. Unfortunately for Gene, waves do not happen a single time. They keep coming and building as the tide comes in.

I did not stop to think that one wave is inevitably followed by another even larger and more powerful, when the tide is coming in.

That inevitability of the situation growing and becoming more dangerous does indeed happen for Gene. The war becomes more real since Leper enlists and then later mentally breaks down. Gene's secret about the branch bouncing comes out, and he's put on trial by his friends. All of this ultimately leads to Finny's death. The wave spoken about in Chapter 8 has intensified and become strong enough to kill.