What about flying fish?

Or fresh water fish or aquarium fish or river fish

But it doesn’t say all fish, does it?

You don't find many working cartographers in prison.

They’re drawing escape plans with semen syphoned from their anuses.

They were chosen first to do it, but they half assed it. All of the fishes took one look at the map and could tell that they did it on the fly.

Too wordy. There's a great joke in there somewhere though.

I wrote it on the fish.