Canada's water becoming gross

I just noticed how much we canucks take for granted that our water is safe and clean. The more places I swim in and drink in though, the more I question that assumption.

I went swimming at Westhawk this summer and caught something. It started out as an ear infection, which I treated. Then I kept getting sicker. I had what seemed like a bad cold, and was told I caught a virus. The doctors never told me what it was exactly, but I got very sick very fast. I was in the hospital because my body wasn't rehydrating. I recovered, thankfully, and am ok, but I suspected it was from the water. Then a friend told me about some kind of bird poop that had made people sick. I never heard or saw anything before this that would have made me think the water might not be safe.

I've had other experiences, too many unfortunately, where I was told I can't trust the water.

I wonder now: how can I know where I can swim, drink, or walk in amongst our lakes and pools? There aren't always signs or warnings. Besides common sense, like not swimming where the water stinks or is visibly 'gross', where can I find out what the risks are? What are reliable sources?

Any advice on how I can become more educated on this issue would be appreciated.