All they need is a hard surface that stays still for 20 seconds, and they'll superglue themselves right on that s**t, covering boats, anchors, motors, lobsters, turtles and even other mussels. Those who can't grab hold of anything wind up washing up by the tons on beaches.
This isn't just inconvenient for turtles who suddenly find themselves weighed down in a sticky mussel flash mob -- the cost to us is catastrophic. In 1989, for example, a city in Michigan lost its water supply for three days because the mussels had crammed themselves into the pipe, cementing it shut.
"We're going to need all the Drano."
Since then, millions of dollars have been spent each year attempting to control the legions of mussels, but we can only slow them down. They can't be eradicated with chemicals without contaminating the water supply, and they multiply too quickly to remove by hand.
In short, these mussels are kicking our asses, which is pretty good for an animal that doesn't know how to move or do anything.
It's like a sit-in protest against the whole of humanity.