"a two foot long fish "or " a two feet long fish" ?
two foot long… or two feet long…?

Question

"a two foot long fish "or  " a two feet long fish" ?
two foot long…  or  two feet long…?

Answer

He got hit with a “ 2 foot long fish”

But in this case...

I caught a baby shark today
How big was it?
“It was 2 feet long. “

So it all depends on how you’re using it

Answer

It's a two-foot long fish.

The fish is two feet long. It's a two-foot long fish.