<a href="https://en.wikipedia.org/wiki/Ripple_Rock" id="mwAQA" rel="mw:WikiLink" title="Ripple Rock">Ripple Rock</a>, an underwater threat to navigation in the <a href="https://en.wikipedia.org/wiki/Seymour_Narrows" id="mwAQE" rel="mw:WikiLink" title="Seymour Narrows">Seymour Narrows</a> in <a href="https://en.wikipedia.org/wiki/Canada" id="mwAQI" rel="mw:WikiLink" title="Canada">Canada</a> is destroyed in one of the largest non-nuclear controlled explosions of the time.