Radio light is not a practically useful way of communicating underwater over large distances. My question is how does one calculate how far a radio wave at a given frequency will propaagate in the ocean before it is made effectively useless by the high dielectric nature of the seawater?
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3$\begingroup$ I'm voting to close this question as off-topic because the exact formula for the attenuation of E&M waves in a conducting material can easily be found in most textbooks on applied E&M. $\endgroup$– ZeroTheHeroCommented Jun 24, 2019 at 14:42
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the standard estimate is that by the time the EM wave has traveled into the water by ~a small fraction of one wavelength, it has been more or less completely absorbed.
This means it is possible to penetrate water to a measurable depth with EM waves of extremely long wavelength- thousands or tens of thousands of meters. Extra low frequency radio has used to send signals to submerged submarines in this way.
answered Jun 24, 2019 at 17:57
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$\begingroup$ Some have said that higher frequency radio waves can penetrate for yards and still be useful. Also, RC submarines exist. $\endgroup$ Commented Jun 24, 2019 at 18:32
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$\begingroup$ do rc subs function in salt water? $\endgroup$ Commented Jun 24, 2019 at 21:11
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$\begingroup$ I could not find any indications that they could function in anything deeper than about 10 feet or so in freshwater. $\endgroup$ Commented Jun 25, 2019 at 0:03
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$\begingroup$ probably zero feet in salt water. $\endgroup$ Commented Jun 25, 2019 at 3:46