They lurk in murky water, eyes just above the surface, looking almost exactly alike. Two big toothy reptiles that everyone mixes up. But crocodiles and alligators are not the same animal — and once you know what to look for, you'll never confuse them again.

Start with the face. An alligator has a wide, rounded snout — broad and blunt, shaped a bit like the letter U. A crocodile's snout is narrower and more pointed, closer to a V. It's the easiest difference to spot once you've seen them next to each other.

Now the toothy part. When an alligator closes its mouth, its upper jaw is wider, so it tucks the lower teeth out of sight. A crocodile's jaws are about the same width, so its big fourth tooth on each side pokes up over the lip — giving it a permanent, slightly crooked grin.

Their skin tells on them too. Alligators tend to be darker — almost blackish-grey, like wet stone. Crocodiles lean lighter, more olive or sandy brown. It isn't a perfect rule, but in muddy water a dark gator and a tan croc do dress differently.

Here's a clue you'd need a science lab to confirm: salt. Crocodiles have special glands on their tongues that flush out extra salt, so they're comfortable in salty coastal water and the sea. Alligators don't manage salt as well, so they stick mostly to freshwater swamps, rivers, and lakes.

Where in the world they live is another giveaway. Alligators are picky homebodies — wild ones live in only two places, the southeastern United States and a stretch of China. Crocodiles are world travelers, found across Africa, Asia, Australia, and the Americas.

There's one rare spot where their worlds overlap: the swamps of southern Florida. It's the only place on Earth where wild alligators and wild crocodiles live as neighbors. If you ever want to compare them in person, that's the address.

So when someone points and says "Look, an alligator!" you can do a little detective work. Wide U-snout, hidden bottom teeth, dark skin, freshwater? Alligator. Narrow V-snout, toothy grin, paler skin, happy in salt? Crocodile.

They've been wearing these subtle differences for tens of millions of years, long before anyone was around to tell them apart. Two ancient cousins, sharing the same swampy family tree — one with a U for a smile, one with a V. Now you're the one who knows the difference.