ICELAND - The Silfra fissure in Thingvellir National Park is a deep, watery crack that separates the North American and Eurasian continents. It's the place where two massive tectonic plates once met and now slowly drift apart, causing earthquakes about once per decade. For many, Silfra is the dive of a lifetime. Not only can you touch two separate continents during your dive, but the frigid glacial water is remarkably blue and astoundingly pure.