The continents make up less than one third of the Earth's total surface and approximately 70% of the crust is covered by water. Approximately 76 species of cetaceans are found within these waters. Cetaceans, also known as whales, dolphins, and porpoises, are intelligent and social animals. There are also 25,000 known species of fish found in these waters. The distribution of marine life is a result of the formation and extinction of species, migration, movement, and competition and balance between species.