The manhunt from a drone becomes more of a nightmare.

Variable pitch! Waterproof! This thing is awesome. Surely there is different tuning when it's in water vs when it's not, right? How do you detect the transition? Motor currents? This is a really neat project!

Obligatory: https://xkcd.com/2128/

Or for the more cynical, replace "search and rescue" with "military covert ops".

SciFi becomes reality.

It's interesting how simple this looks, off the shelf parts, and 3D printed components. I'm almost surprised this doesn't already exist after looking at it.

I suppose that pool is the ~max RF range under water? Is prop pitch mandatory for underwater use?

Any ideas how the signal is transmitted once the drone is underwater? Typical RC transmitters run 2.4 GHz. Some systems use 700 MHz. The former wouldn't penetrate at all, the latter might penetrate to a shallow depth, but I think that what's shown in the video is deep enough that the signal would get attenuated. There doesn't seem to be a tether and the drone doesn't seem to have any computer vision capabilities to fly itself whilst under water. I wonder how they solved this.

Very impressive. I assume that underwater propulsion uses a lot more energy per meter moved?

Maybe you will be able to us these to defend Greenland?