Ripple Rock Explosion April 5th 1958

Ripple Rock was a reef less than 3 meters below the surface of Seymour Narrows. It was a major navigation hazard and caused about 120 shipwrecks between 1875 and 1958 killing at least 110 people.

There had long been plans to try and remove it somehow.

Between November 1955, and April 1958, a three-shift operation involving an average of 75 men worked to build a 174 metre vertical shaft from Maud Island, a 762 metre horizontal shaft to the base of Ripple Rock, and two main 91 meter vertical shafts into the twin peaks, from which “coyote” shafts were drilled for the explosives. The contract was awarded to two firms for $2,639,000. At the time of the contract it was estimated the tunnels and shafts would not be completed until either 1957 or 1958 1,270 metric tons of Nitramex 2H explosives were placed in these shafts, estimated at ten times the amount needed for a similar explosion above water.
The explosion took place at 9:31:02 am on April 5, 1958. 635,000 metric tons of rock and water was displaced by the explosion, resulting in debris at least 300 metres in the air, falling on land on either side of the narrows. The blast increased the clearing at low tide to about 14 metres (45 feet).
The Royal Canadian Mounted Police cleared the area of within 3 miles of the explosion, and the engineers and TV crew that witnessed the explosion were housed in a bunker

It remains to this day one of the top five planned explosions in human history.
https://en.wikipedia.org/wiki/Ripple_Rock