User blog comment:Staw-p/Caribu pirates still alive?/@comment-1595565-20111216222434

It's not a matter of depth, it's that they were unconscious and therefore couldn't hold their breath. Even if they did get a good gulp of air before their ship got wrecked, they would have had to hold it while ascending 7 km while dealing with all the fun creatures encountered along the way plus pressure sickness and temperature.