The important issue with VLF radio in this case is that what we need is sub->ship communication. VLF relies on massive antenna, often ground based to (very slow

The important issue with VLF radio in this case is that what we need is sub->ship communication. VLF relies on massive antenna, often ground based to (very slowly) send message to subs. My understanding is that for comms the other way, the sub needs to raise an antenna above the surface (then possibly doing laser comms to a satellite so that no radio emissions give away sub locations).