Does water really amplify radio signals? What is the energy source? Does the water cool down? Does it works for Wifi?
Is salty water better or worse as an amplifier?
Where did you acquire the idea that "water amplifies radio waves"? Water in its natural impure form is usually conducting and damps radio waves and the saltier the more conductive it becomes. There exists no solid, liquid or gas that amplifies radio waves (Even in a maser you have to supply energy.)