With deep sea fuck ups, you generally don't know anything before you're dead.

The only exception is if a legit submarine (double hulled, navy warship type) has a problem, and people get trapped in compartments and run out of air.

With how shitty this one was? It popped, and they didn't have time to realize they were dead before they did. Iirc, 30+ atmospheres of pressure, and it's enough force from the water to pulp you instantly.