I never realized the post was making a joke about the OceanGate sub until just now reading another thread.

At the time, June 2023, they were searching for the missing sub and thought they could have 3 days to survive. So OP was probably making a dark humor joke about how to avoid shitting in the sub.

But they were so vague that it had everyone - myself included - speculating on why someone wouldn’t want to shit for that long.