Half of the oceans are just vast open sea, stretching seemingly endlessly till the nearest land or island, rarely providing nourishment or shelter. It's roamed by good, nearly tireless swimmers. Yet many swim in large schools, to make best use of rare feeding opportunities - thus when a school of small fish surges from the deep sea, dolphins, mackerels and sword fish race to corner and devour the prey. Whale calves must wait hours while mothers dive to he deep sea bed. Unlike mostly rapid predators, may prey species float, which currents may carry anywhere over years, but like jellyfish reproduce massively reaching rich waters.
—KGF Vissers