Thunder and lighting

He accepted it, but then hung around in the background to watch us anyway. At last Chris hauled the apparatus up out of the water, dried it off and showed it to him. As soon as the crewman recognised that it was a condom we had been dangling in the water it seemed as if some light dawned. 'Ah!' he said. `Ficky ficky!' He grinned happily and plunged his forefinger in and out of his other fist. `Ficky ficky!' `Yes,' we agreed. `Ficky ficky.' Pleased that all was clear now, he wandered off and left us to it as, each in turn, we listened to the tape over headphones. The sound we heard wasn't exactly what I had expected. Water is a very good medium for the propagation of sound and I had expected to hear clearly the heavy, pounding reverberations of each of the boats that had gone thundering by us as we stood on the deck. But water transmits sound even better than that, and what we were hearing was everything that was happening in the Yangtze for many, many miles around, jumbled cacophonously together. Instead of hearing the roar of each individual ship's propeller, what we heard was a sustained shrieking blast of pure white noise, in which nothing could be distinguished at all ...»