In Europe? Bing-powered Water Watch shows you where it's safe to swim
Fortunately for you, Microsoft and the European Environment Agency have just the thing for you. The Eye on Earth Water Watch does exactly that for countless spots across the continent.
Find a suitable spot, click the water quality icon, and the Bing-powered map displays an overlay containing a Virtual Earth image as well as live webcams and user submitted photos (if available, of course).
There's more to it than finding a place to have a relaxing dip, of course. As Microsoft's Rob Bernard puts it, "Eye on Earth is a great example of how technology has the power to help governments, business and individuals understand what is happening to our environment. Eye on Earth provides people with information which has historically been difficult to find."