They pelt along the line of pumping stations, some lit and gurgling, some dark and silent. The latter outweigh the former, but the proportion is shifting as the tide rises. Mark stops at one unlit station, indistinguishable from the rest, and points. "In there."

"Shit," breathes Miles, his head filling with visions of horror. The pumping chambers are uniformly the size of a large closet, and filled with water when in use, air elsewise. Their watertight access hatches must be almost totally soundproof. No sound at all except, eventually, the rush of rising water...

"I know," says Mark, tight-voiced with some unidentified mixture of emotions, and he taps at the controls for the hatch and then hauls on the locking bar. The door yields to applied pressure and swings inward. Miles rushes forward with handlight and rappelling harness.