Maybe it was a great hank of river weed turning below in the cold current, maybe it was just the way gravity works in water, but it felt like something that matched me exactly, the same shape and weight and volume, and it always seemed as if that something came to life the moment I stepped into the water.
They found that gravity waves "break" on the surfaces of planes, justlike ocean waves breaking on the beach, causing much of the turbulence that occurs out of the blue in clear air.