The question came to mind after reading a new bit of Creationist nonsense PZ Myers came across. You'd think anyone above about oh, the age of three would know that urine is the result of fluid intake, and therefore largely composed of water. Apparently not whoever came up with this silliness.
(If you read the comments to PZ's post you'll see a lot of people think it's a Poe. Whether it is or not you can be sure someone out there does actually believe this.)