(Narrator) What is this creature taking a bite out of your toe?

(Beachgoer) Ow!

(Narrator) And ruining your day at the beach?

Some people call them sand piranhas.

Scientific name: Excirolana chiltoni.

These tiny crustaceans are on the prowl for protein, and they don’t care where they get it.

From dead animals – like this pipefish –  that washed up on the shore, to beachgoers’ flesh … in this case, your ankle.

One bite feels like the nick of a razor blade – sharp and then stinging.

But with enough time, a large group could likely clean the flesh straight off ya.

Here's one, biting away at a foot, spinning in a full circle to get as much of you as it can.

They’re relatives of roly polies, which actually evolved from ocean animals.

Excirolana chiltoni are found in shallow waters on the coasts of places like Canada,   the United States, Japan, Taiwan and Hong Kong.

But because they’re tiny, travel in small groups and have sand-colored camouflage,   they’re pretty easy to miss.

Sand piranhas live in the swash zone, where saturated sand is washed over by waves.

Out of the whole wide beach, they stay  in a band about the width of a car.

Once in a while they get stuck in a tidepool.

But mostly these crustaceans  burrow in wet sand between waves … … taking cover from predators  like these shorebirds.

The sand piranha digs in with some fearsome tools.

It holds steady with these hooks on its legs, then deploys this pair of mandibles.

They scrape away at their meal.

And these front legs, called maxillipeds, sweep food into its piehole.

And right now, you're on the menu.

It doesn’t even try to ease  your pain with anesthetic.

How rude!

And once it's down the hatch there's no hiding what it had for lunch.

Don’t worry!

That’s not human blood.

This sand piranha is chowing down on something called a bloodworm ... … named for its bright red worm blood.

Sand piranhas travel up and down  the beach as the tides change.

Few creatures can survive the rough-and-tumble life here in the swash zone.

So these crustaceans get priority access to whatever washes up.

They help clean up all kinds of wayward corpses, like this sea pickle ... ... keeping your favorite beach  a little less stinky.

Now, you don't have to wait 'til one of these tiny piranhas  starts chomping on your foot to know they’re around.

Watch out for these distinctive scribbles in the sand.

If you see them, keep moving your feet through that swash zone.

Or better yet – dive in.