I used to work for an entity that built UUVs (or underwater drones), which were really neat. They used them to test sonar systems.
That said, they're likely very different in how they work and the components to achieve that (flight vs swim) but I'd also imagine that a lot of the communication systems would be similar. So... if someone were to ask a question about them here would that be in scope?
Considering the name of the site, it's possible it won't ever happen... but when I saw this proposal, this was the question I had.