After "trembling with horror" before attempting his passage through the long tunnel under the rock and the sea, Jerry puts on his goggles, testing the vacuum, then he fills his lungs and sinks to the bottom with the stone that he holds. It is not long before he is inside the tunnel, and he bumps his head, causing him a sharp pain. However, Jerry's worst moment occurs after his false sense of victory in seeing a crack of light. For, darkness lies ahead and his lungs begin to hurt as his oxygen supply depletes.
He must go on into the blackness ahead, or he would drown. His head was swelling, his lungs cracking....He felt he was dying.
Jerry continues to count and loses some consciousness, but he perseveres between these lapses until, finally, there is "an explosion of green light" as Jerry surfaces, "gasping like a fish."