The American Crocodile is the only New World crocodile and the top predator in its range.

Like all crocodiles it is a quadruped, with four short, splayed legs; a long, powerful tail; a scaly hide with rows of ossified scutes running down its back and tail; and mighty jaws. It has nicitating membranes to protect its eyes, and, despite the myths it does have lachyrmal glands, and can cleanse its eyes with tears.

The nostrils, eyes, and ears are situated on the top of its head, so the rest of the body can remain concealed underwater. The coloration also helps them hide.

American Crocodiles normally crawl along on their belly, but they can also "high walk". Smaller specimens can gallop, and even larger crocodiles are capable of surprising bursts of speed. They can swim equally fast by moving their body and tail in a sinuous fashion, but they can sustain this form of movement much longer.

They have a four-chambered heart, like a bird, which is especially efficient at oxygenating their blood. They normally dive for only a couple of minutes, but will stay underwater for up to 30 minutes if threatened, and if they remain inactive they can hold their breath for up to 2 hours. They have an ectothermic metabolism, so they can survive a long time between meals — though when they do eat, they can eat up to half their body weight at a time.