100days-a-year
Contributor
uhhh,Runvus ULF sound waves or ULF radio waves.Milatary has used ULF radio for decades to communicate with subs.ULF sound(a lond distance sonar form)has been implicated in beachings and deaths.It is a relatively new technology now mostly unneeded due to our far superior hunter/killer subs and some other toys we have.The EyeSea and similar are pretty cool ,but if you need that to know where you are in relation to the boat I'll pass on having you dive with me.