Baring rows of serrated teeth, a great white shark is aptly called a killing machine. Researchers believe great whites hunt visually, sighting their prey, ramming into it, and stunning it while biting into it at the same time.
Try using your camera vertically instead of horizontally from time to time. Notice how dramatically it changes what's included in the frame. Often, shooting vertically can clean up messy backgrounds and help better define your subject.