You could more or less film anything moving in super slow motion and it looks cool, but underwater explosions in super slow motion really are something else.
The Slow Mo Guys simply placed a lit "m-1000" firework into a water tank and filmed the results. At a normal frame rate, the 0.01-second long underwater explosion looks like a piddling little pop. But at 120,000 frames per second, the explosion is a mesmerizing cosmic blast, which then collapses in on itself under the pressure of the water.
Check out it below.