Chicago engineer Matt Mikka of Warped Perception (previously) built a model rocket with the intention of launching it under water. Mikka first submerged the engine only and the rocket launched successfully.
Just for fun I decided to build a model rocket and launch it from underwater while filming it with the high speed camera in slow motion.
He then fully submerged the rocket to see if it would be just as successful. And it was.
He proceeded to capture the launch from every angle in 4K slow motion.