One use case I think would be really great for drone-fish would be programming them to be able to search for warmer-than-the-water objects on the surface and sw

One use case I think would be really great for drone-fish would be programming them to be able to search for warmer-than-the-water objects on the surface and swim to them, to potentially find people lost-at-sea. Then, ideally it could have a blow up life jacket or some such along with an ability to transmit a radio signal to an emergency channel. You'd of course need a whole lot of these to make any noticeable effort at actually reaching people, but it'd be worth it if the cost of these got low enough.