How sharks reproduce varies and can include laying eggs in secluded nursery waters or giving birth to live pups after the lengthy internal gestation of eggs, but all sharks mate via internal fertilization during copulation. Nurseries are warm, shallow waters where young sharks are safe from large predators and can feed on the plentiful fish around them before swimming out into the open sea.
Sharks mate so that the male can fertilize the female's eggs. The two sharks the leave one another immediately after copulation. The eggs develop for a time within the female shark's belly.
Some sharks will lay their eggs in the nursery waters. These waters give shark pups a strong chance of surviving to adult size. In the open ocean, they could fall prey to grown sharks and other predatory fish, but with a steady food supply and warm conditions, they will grow quickly and be able to fend for themselves.
Other species of shark keep their eggs inside their bodies until the pups hatch. The sharks then give birth to their pups in a process similar to mammalian live birth. Pups born this way run no risk of being killed while waiting to hatch and are ready to be on their own from birth.