One of the most powerful defensive charms known to wizardkind, the Patronus can also be used as a messenger between wizards. As a pure, protective magical concentration of happiness and hope (the recollection of a single talisman memory is essential in its creation) it is the only spell effective against Dementors.
The wave visible above the level of the water is in fact only part of the wave; the wave extends down through the water column to the ocean floor as well. Waves start out in the deep, open ocean as relatively vertical in shape, Presnell said. As a wave travels toward the shore, though, the bottom part of the wave drags along the ocean floor. The upper part of the wave above the water line starts to move faster than the rest of the wave. As the ocean depth decreases closer to shore, the drag on the wave's bottom becomes stronger, and the upper part of the wave begins to tilt forward.
The highest part of the wave is called the wave crest, and the lowest part of the wave is the wave trough. Waves travel together, and this movement of waves as a group is known as a wave train. There are different types of ocean waves. Wind waves are waves that are created by wind.