Following that same line, if we had that ability, it would be useful for communicating to deep submarines like the U.S. used to do with Project Sanguine[0] and

Following that same line, if we had that ability, it would be useful for communicating to deep submarines like the U.S. used to do with Project Sanguine[0] and ELF waves :) [0] https://en.wikipedia.org/wiki/Project_Sanguine https://en.wikipedia.org/wiki/Project_Sanguine