What is the Submarine Communication...?

What is the Submarine Communication and Radio Navigation ?

Radio navigation is the application of radio frequencies to determine a position on the Earth. Like radiolocation, it is a type of radio determination, whereas Submarine is a watercraft capable of independent operation underwater. The communication between these Submarines is called as Submarine Communication.
So, VLF (Very Low Frequency) is used for long range Radio Navigation and Submarine Communication.