The Goblin Shark is a fascinating — not to mention slightly freaky-looking — creature, and this is a great video of one doing it's thing, including some good footage of it's signature protrusible jaw. Take a look after the fold.
Click here to view the embedded video.
When it's not being used — unsuccessfully — to fend off annoying divers, that jaw shoots out to grab small, fast moving prey that has been detected by the battery of bio-electrical sense organs in the elongated snout. It's much more energy efficient than trying to move an entire 11' shark at the same speed, and probably also helps to bring the jaws, which would otherwise be obstructed by the snout, into a useful biting position.
Hat-tip to Cephalopodcast for the video. (There's also some interesting stuff about Megalodon (possibly the largest predator the Earth has ever seen) at that link, in case you missed it in the news recently.)