Neat stuff. Still needs tethering, which makes sense while it's being developed.

However, reality is no match for imagination. When I was a kid the TV show Voyage to the Bottom of the Sea was popular. One of the absolute coolest things was the Flying Sub[1][2]:

   36 foot wide and long, flying submersible,
   aptly called the "Flying Sub"
   ...
   It was deployed through bomb-bay like doors.
   As it broke the surface, its engines could
   generate enough thrust for the vehicle to
   take off and fly at supersonic speeds.

[1] https://en.wikipedia.org/wiki/USOS_Seaview#Refit_and_the_Fly... [2] https://www.youtube.com/watch?v=WHNNXVZ1mYg