How do you tell if a Great White Shark is a boy or girl?

If you are able to handle the shark, flip it over on it's back. Look on the underside of the shark, right in between it's lower fins by the tail. You will see the genitals. Male nurse sharks will have long fin like appendeges hanging on both sides of the genitals. These are called "claspers". These aide the male in mating with the female. Female nurse sharks will not have these claspers.