Having spent roughly 30 years of my life living near the Potomac River I've spent many a day boating and swimming on the river.  (Side note: I've never owned a boat in my life and am a firm believer that boating is best enjoyed when someone else's boat is involved).  I'm having serious doubts about ever swimming in it again for two very good reasons: the presence of the Snakehead, a catfish that can literally walk across land and has rather large teeth, and the fact that an eight-foot bull shark has been caught in the river.   

If you need me you'll find me by the pool.