I've actually never drank out of a puddle, but I imagine it would taste like unflavored coconut water.
Now, enter flavored coconut water and Hello Dolly! I'm hooked. It's fantastic - a great pick me up in the afternoon when I think I don't have any more energy to work. I really like the coco cafe drinks (vanilla is my fav) in a glass with ice. Ice is definitely a prerequisite to fight off the stagnant puddle water taste, by sure why that is, but for my tastes, I need ice. Which is kinda funny since I drink 2-3 large nalgenes of water per day sans ice, just cold water via the Brita filter.