When you’re sitting on top of the water far from the surf and the air is calm the ocean seems to be a quiet place. If you were to dip your ear into the water, as Lynn Schooler does with a hydrophone off the Alaskan coast, hoping to locate the schools of herring that draw the hungry humpbacks to feed, you would hear a lot:
“I listened for the light, hissing static that can signal the presence of herring. The clicks and pops emitted by millions of tiny gills create a distinct underwater ‘signature’ that can sometimes be heard for miles and – if we were lucky – might be accompanied by the baritone rumbles and high-pitched squeals of hunting whales.
“The hydrophone chortled and whispered in the myriad voices of the ocean: a ratcheting whir – the voice of a porpoise using echo-location to feel its way through the depths; the hiss of strong currents stirring sand along the bottom; the innumerable tiny crackles and snaps that rise from hordes of crab, shrimp, bivalves, and unnameable bottom-crawling creatures; odd, indecipherable sounds that added to the depth of mystery in the black world beneath the Swift’s keel.”
source: The Blue Bear by Lynn Schooler