Ripple Rock was a submerged twin-peak mountain that lay just nine feet beneath the surface of Seymour Narrows . It was a serious hazard to shipping , sinking 119 vessels and taking 114 lives . The gunboat USS '' Saranac '' was one of the rock 's first recorded victims . On April 5 , 1958 , after twenty-seven months of tunnelling and engineering work , Ripple Rock was blown up with 1,375 tons of Nitramex 2H explosive making it the largest commercial , non-nuclear blast in North America . The Halifax Explosion in 1917 was larger but it was not a deliberate act
Halifax Explosion
Halifax Explosion
Seymour Narrows