Hi syed fareed,
I totally agree with Remo’s answer, I want to add that from the name itself it is specially designed for free space Optical communication that has a Refractive index (RI) of 1 but in case of water RI=1.33 This is a vast difference accordingly the speed of light will be lesser in water all the optisystem component property will not natch with it due to this difference. an turbulence and viscosity of fluid will be a major factor to be considered here.
Regards,
Dhiman