How did I not know that lakes could have shellfish?

Living in the Maritimes for my entire life until this point (save a spell in Japan a number of years ago), I honestly thought shellfish only came from the sea.  Sitting on the beach at Sandbanks National Park this summer, though, I discovered broken pieces of shells amid the sand.

And here, on a rocky shoreline, were these shiny pink clam shells.

You learn something new every day.