The Crystal Caves are in Bermuda, and getting into the main one takes you ninety-odd steps down into cool, still air. They end on a pontoon bridge floating directly on Cahow Lake, held up by nothing but water. The lake is open to the ocean through flooded rock, so the planks under your feet rise and fall through the day with the tide outside. It is seventeen metres deep and clear to the floor beneath you. The air holds about 22 degrees whatever the weather is doing above. The ceiling is crowded with soda straws — thin hollow tubes of limestone, each built one drip at a time. They carry on below the waterline, standing in the seawater.
Nothing down there was made underwater. Those formations grew in open air, when the sea around Bermuda stood far lower than it does now. Rainwater working down through soft limestone hollowed the chambers out and built the straws drip by drip, and when the sea came back up it drowned the lower cave. The water under the bridge is not empty either. Bermuda's flooded caves hold blind, near-transparent crustaceans — about sixty-five of the seventy-eight species recorded in them live on this island and nowhere else, several known from a single cave. They keep to galleries that only cave divers reach, well past the lit stretch of lake you are standing over. Almost all of the island's hundred and fifty known caves are crammed into one patch of ground, two square kilometres of its oldest limestone. Crystal Cave is simply the one that got a stairway and lights; Fantasy Cave next door, shut for some sixty years and reopened in 2001, runs to amber and cream where this one is white. Nobody was looking for any of it. In 1907 two twelve-year-old boys chased a lost cricket ball to a hole no wider than a coin, with warm air coming out of it. They went in after it.