Last Exit from the Secret Sea

> It was estimated that the water would reach us in about 30 minutes. We continued with our breakfast, unaware of the seriousness of what was coming our way. Then, without warning, the water hit us.

Without warning, you say?

I guess they meant without any immediate tangible evidence that water is actually going to hit them, but there definitely was a warning.

Is it common to get false alarms or to wait it out and see when getting informed of a flood? At face value it just seems reckless, but I don't know enough about cave exploring to judge.