[Pollster1]

There is no way to communicate effectively with a sub at -2000 meters. And if it rises to 150ft to put out a long wire it's likely to lose contact with it's target.

Wouldn't communications depend on data rate and transmission frequency? I would expect ELF to reach deep from land-based transmission sites but with a low data rate, and sound to reach deep at a higher data rate from the surface ship.

[Mariner]

Even with VLF and ELF, there are depth limits...less so with ELF.

Still, there no way the drone could TRANSMIT anything useful as they don't have 5-10MW and a 5mile antenna to work with.