In many areas of fast-flowing water, a boat could be turned over by a wave as high as a house.
VOA: special.2009.10.07
As each wave came, the boat rose and fell, like a horse starting toward a fence too high to jump.
VOA: special.2010.03.06
The first is a decline from the high ( wavea ) that was followed by a rally (wave b ) that typically will stop below the 61.8% retracement resistance of wavea.