We are at the bottom of an enormous volcano, but this one is active! The huge amount of water beneath us protects us from the heat of the lava far below. But the water is growing warmer. And it's rising.
Days pass. Every hour we move higher, and the water grows hotter. This volcano is getting ready to erupt and we will be vapourised! We find a packet of biscuits, the only thing that survives from our luggage. We haven't eaten in days. We can't last much longer. If we leave the biscuits for one more day we can maybe stretch our lives by another 24 hours. Or should we eat them now, giving us strength in case we need to act quickly? Or do something else?