The term 'of ocean motions' can be summarized by the crossword solution 'TIDAL, ' which refers to the regular rise and fall of the ocean's surface due to the gravitational pull of the moon and sun. Tides are caused by the difference in gravitational force between the moon and the sun, and the resulting bulge of water on the side of the Earth closest to the moon. Tides are an important part of ocean life, as they provide a source of food and nutrients for many marine organisms.