There are these two young fish, so the joke goes, just swimming along, slacking off. They see an older fish in the distance, swimming towards them from the opposite direction. As the older fish passes, he waves his fin at the youngsters and says,
“Morning, boys, how’s the water?”
The two young fish swim on a way, in silence, then finally one turns to the other and says,
“What the hell is ‘water’?"