My Watermark is the Toronto Harbour of Lake Ontario.
I spent the weekends last summer distance swimming on the outside of the island, from the airport buoys to Gibraltar Point and back (4km, over 2 hours at my slow speed). The water was gloriously clear. But it's not like that everywhere.
One day I heard the lifeguards listening to their radios for the daily E Coli counts for all of the beaches. Hanlon's, where we were, was 10, much lower than the cut-off of 100. Marie Curtis Park, in the west end close to where I work and where I would love to be able to swim, was 900, a giant cesspool. So I'm stuck biking and paddling an hour out of my way in order to swim without getting ear, throat and skin infections.