It’s a Scottish saying, essentially expressing optimism about the future. Seems appropriate at this moment as I write this: Closing out not only a year but a decade. It takes a pretty optimistic people to commit themselves to the production of something that takes decades (in some cases) before it is ready to sell. Applause!
Not all water is lucky enough to fall on Scotland. Whisky is the water of life, and you could say that whisky is what water dreams of becoming when it grows up. 😉