Underwater explosions are, in general, much more dangerous than those in air. This video shows an underwater blast at 30,000 fps. During the initial blast, a hot sphere of gas expands outward in a shock wave. In air, some of the energy of this pressure wave would be dissipated by compressing the air. Since water is incompressible, however, the blast instead moves water aside as the bubble expands. Eventually, the bubble expands to the point where its pressure is less than that of the water around it, which causes the bubble to collapse. But the collapse increases the gas pressure once more, kicking off a series of expansions and collapses. Each bubble contains less energy than the previous, thanks to the loss of pushing the water aside. (Video credit: K. Kitagawa)
If you needed something to make a science GIF out of this weekend, here’s a good subject.