I spent some time in the Navy. I don't recall being tested for my ability to swim. It does seem odd doesn't it! We all just took it for granted back then....They herded us into the freezing water - we swam. What else? When things changed, I think most still assumed that everyone could swim, when in fact they couldn't. I recall the story of one guy falling off the boat in the harbour - his buddies on deck had a good laugh, until they saw the only thing coming up were bubbles...