Ripple Rock (French: Roche Ripple) is an underwater mountain located in the Seymour Narrows of the Discovery Passage in British Columbia, Canada. It had two peaks (2.74 metres and 6.4 metres below the surface at low tide) that produced large, dangerous eddies from the strong tidal currents that flowed around them at low tide. Ships transiting the strait preferred to wait until slack tide in order to safely bypass the rock.The hazardous nature of the rock prompted the Canadian government to remove the top of the mountain in a controlled explosion on 5 April 1958. The event was one of the first live coast-to-coast television broadcasts of an event in Canada and was designated a National Historic Event of Canada.