What are the advantages of internal fertilization of animals over external fertilization?

In the process of external fertilization, male and female gametes are excreted into the external environment. Since a large number of germ cells die from unfavorable environmental conditions, living things have adapted to produce a colossal number of gametes to increase the chance of fertilization.
Internal fertilization occurs in the body of a female by introducing male gametes into her reproductive tract. In this case, the probability of fertilization is an order of magnitude higher and the number of gametes is much lower. Also, with such fertilization, the survival rate of a fertilized egg is also much higher.