Conversely, like many other reptiles, they can spend long periods in more xeric conditions. It's not unusual to find a saltwater croc on dry land hundreds of miles inland from the coast. The saltwater crocodile is able to inhabit saltwater because they have glands that secrete salt, thereby keeping the salt level in their blood lower than the salt level in the ocean waters. They are at home in both fresh and salt water. Most other crocodilians inhabit major river drainages, and stick to freshwater habitats.
Alligators are crocodilians, just a separate group like caimans or garials.
Interestingly, there are only two alligator species in the world, the American alligator and the Chinese alligator. They are sister species, with their ancestor occupying north america and asia millions of years ago when the area of alaska and the bering straights were a connected, tropical land. When the climatic barrier formed between North America and Asia, the two alligator species evolved independently. I understand that it was on the endangered species list from 1967-87. The school assignment is to gather raw numerical data.