Snippet from the speech -

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?"

This is a standard requirement of US commencement speeches, the deployment of didactic little parable-ish stories. The story ["thing"] turns out to be one of the better, less bullshitty conventions of the genre, but if you're worried that I plan to present myself here as the wise, older fish explaining what water is to you younger fish, please don't be. I am not the wise old fish. The point of the fish story is merely that the most obvious, important realities are often the ones that are hardest to see and talk about. Stated as an English sentence, of course, this is just a banal platitude, but the fact is that in the day to day trenches of adult existence, banal platitudes can have a life or death importance, or so I wish to suggest to you on this dry and lovely morning.