Why did the shellfish get kicked out of the gym?

It already had plenty of mussel.

Did You Know?

"Mussel" sounds like "muscle" — so the shellfish didn't need the gym because it already had plenty of muscles (mussels)! Mussels are incredibly strong for their size, using byssal threads (sometimes called "beards") to anchor themselves to rocks with a grip so powerful that scientists study them for creating surgical adhesives. A single mussel can filter up to 15 gallons of water per day!