In October last year I made my first audio recording of the Firth of Forth from a diving rib that was around 500-600 metres away from the main deep shipping channel. My hydrophone was at approximately 20 metres in depth and highlights that the attenuation of sound through water is extremely efficient. As I was making the recording, a large tanker appeared further up the estuary a couple of miles away, the noise of its engines slowly increasing until it was quite overpoweringly noisy.