"Later," Simon continued, "you set it off and measure the result. What is the result? Well, the water above the explosion is going to bulge up. From there, waves are then going to spread outward. To give you a feel for magnitude, a standard shipping container full of TNT gives you rather more than a tenth of a kiloton of explosive yield. In round numbers, it would require a hundred of those to give you a Hiroshima-sized explosion. But even a single one, if the water isn’t too deep, will produce a bulge and a system of waves."