Reaching crush depth wouldn’t be a slow crushing. Once the first deformations appear in the pressure hull, the whole thing caves very very fast, likely over the course of a couple seconds at most, depending on the pressure when it finally gives (44psi per hundred feet, at 1800 ft would yield almost 800psi, that’s a lot of pressure, and a massive release of energy once the hull finally gives.).
The strength of the hull comes from its shape more than material strength (though that does play a massive factor).
What feels slow, and would feel like an eternity, would be everything that leads up to crush depth.
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