Most fish suck in their food. They open their mouths and water rushes in, dragging the meal with it. Moray eels can’t do that - their bodies are long and thin like snakes, so the suction trick doesn’t work for them.
Instead, evolution gave them a second jaw. Hidden inside a moray eel’s throat is a smaller set of “pharyngeal jaws” with teeth of their own. When the eel bites prey with its main jaws at the front, the inner jaws shoot forward, grab the prey, and yank it down into the throat. Then the outer jaws can let go.
The whole movement looks shockingly familiar to anyone who’s seen the Alien movies - and it’s been suggested (though never confirmed by the filmmakers) that the moray’s hidden second jaw inspired the famous Alien’s two-stage mouth.
