Fire in the hole!
Count Me In: Igniting Gas-Filled Air Rings Underwater

This is a video of the Backyard Scientist constructing a device to blow consistent air rings underwater, then pumping oxygen and propane through the system to create flammable GAS rings, then using a homemade underwater cattle prod to ignite those rings and film the results in slow-motion. Heck yeah, underwater rings of fire! Hit it, Jonny Cash. “♬ Because you’re mine, I walk the line ♬” Dammit no not that one.

Keep going for the video, but the real action doesn’t start until 8:30, with the best explosions following shortly after.