The Golden Spider by Francis Lynde

The flood in the cave, already three or four inches deep on the floor and pouring out of the entrance in a splashing cataract when the three boys made a mad scramble for the mine tunnel, rose swiftly to a roaring, bellowing torrent as they stumbled in black darkness up the inclined drift and crowded themselves into the highest part of the heading.

How long the imminent threat of death, either by drowning or stifling, lasted they could never tell, though minutes can easily figure as hours under such terrifying conditions. But one thing they were made quickly to realize, and that was that the upward pitch of the tunnel was all that was saving them from being drowned, like rats in a trap. A sudden, half-suffocating increase in the air pressure, making their ears ring and their hearts pound like laboring pumps, told them that the water had risen above the mouth of the tunnel in the main cave and was compressing the pocketed air. And it was the subsidence of this pressure that first gave them assurance that the worst was over――that the fury was expending itself.