A tunnel
His feet were presumably always cold because of this. He could feel air rushing through his floorboards all the time. The tube now appeared to be his only exit from this pitch-black space. He was beginning to feel claustrophobic, so he realized he needed to move quickly.
Crawling through
David inhaled deeply before turning on his flashlight. Then he began to move through the brief, confined tube. Because the tunnel was too narrow for him to walk through, he had to crawl through it on his hands and knees. David crawled out despite the soil’s cold and wet conditions.