I’ve used this before. But I want to use it again; it’s increasingly relevant and I can give credit to the person who came up with it.
There are these two young fish swimming along and they happen to meet an older fish swimming the other way, who nods at them and says “Morning, boys. How’s the water?” And the two young fish swim on for a bit, and then eventually one of them looks over at the other and goes “What the hell is water?”
David Foster Wallace, in 2005 Commencement Address to Kenyon College
What is our water, and how has it changed?