Because they don't swim in pairs. Are there two of those fish? Nahhh.
A scarfish
Oh, you guessed it right... the tuna fish!
Because he left the school.
Panther no pants, I'm going swimming!
He held up a pair of pants!
At a Pair of Docks
They keep getting caught in the net!
You can tuna piano, but you can't piano tuna.... What about the pot of glue I knew you'd get stuck.