What's inside a clam? A retractable foot ... At first, we didn't have much luck. Benji: I got one, but it looks like it's dead. Soren Dahl: Old shell. Benji: Oh, I got a crab.

If you've ever gone to a seafood market or small fishmonger to buy your shellfish, you may have noticed that clams ... and do their thing -- that is, filtering water through their open shells.