Why do crocodiles live in rivers and not sea?

As the name "salt water crocodile" might tell you, crocodiles can live in the sea. This goes for Nile crocs too. They sometimes show up in the Comoros, a small island group more than 700 miles from mainland Africa and more than 500 miles from Madagascar, that has a small Nile crocodile population.

The Australian "salties" are even more adventurous, known to have showed up the Sea of Japan, a 3000 miles swim from the closest decent saltwater croc population.

Still most crocs live in freshwater or in deltas with brackish water. But it is not uncommon for them to take "day trips" into the sea and coastal areas.