You can check the attached papers;

Sir the recommend papers by you is already solved. I am also having solutions for the above paper. I want to know the basically how the frequency will be available in Underwater environment.

Anyhow thank you sir for your kind answer Abedallatif Baba

It is to be realized here that frequency analysis scales down the measured value which makes measurement with higher precision when compared with time domain measurements, hence frequency measurements should be used when higher precision is required. Normally, frequency meters with higher precision are available in market which should be able to do the underwater measurements.~KS

Thank you sir for your kind reply to my question Srikanth Kavirayani