Never fear! In the spirit of learning new things, here's a tutorial to help walk you through! Since the vast majority of mussels are farm-raised and then held in tanks to flush out grit an impurities, it's not necessary to soak mussels in water at home. If you're unsure, ask the fishmonger when you buy your mussels.
As you clean and debeard the mussels, check to make sure their shells are tightly closed. Discard mussels with cracked shells. If any mussels are open, tap them gently against the counter and discard any mussels that don't close up within a few minutes.
Scrub each mussel individually, trying to remove as much of the stringy bits clinging to outside as possible.
Look at the crack where the two shells meet and you'll see a little 'tag' of what looks like threads of brown seaweed. This is mussel's "the beard" (a.k.a. the Byssus Thread, for the biologists among us). The beards on some of the mussels may have been removed during processing, so it's ok if you don't find one on every mussel.
Pinch the beard between your thumb and first finger. Use a side to side motion and firmly tug the beard out. This can feel a bit like a game of tug-of-war between you and the mussel!
The beard isn't harmful or inedible (just not particularly desirable to our taste buds), so don't fret if there are a few little threads left that you can't grasp.
With a bit of practice, cleaning and debearding a few pounds of mussels should only take about 15 minutes of your prep time.
Any questions? We're here to help!
Related: Ocean Friendly Seafood Guide
(Images: Emma Christensen for the Kitchn)