Light vs Radio attenuation in water

[Major25]

Hi all,

I can't figure this one out, but I'm sure I'm probably missing something simple. Here's the problem I'm having: From what I've been told in my SCUBA class (as well as from online article's and forums) light is attenuated in water in the order red->violet (red being attenuated first). Red light has longer wavelengths than violet light, so this leads me to believe that longer wavelengths are more attenuated underwater than shorter wavelengths.

However, it was my understanding that if radio towers wished to communicate with a submarine underwater, they can only barely make it work if they transmit at low frequencies (longer wavelengths), and not at all at higher frequencies. THIS leads me to believe that lower frequencies are less attenuated in water, which is contradictory to the first paragraph.

What is it that I'm missing from this picture?

Thank you very much, this has been bugging me for a while.

 

[nasu]

The relationship you mention, the absorbtion decreasing with increasing wavelegth is a very local one, it happens for some regions of the spectrum but cannot be extended to the whole spectrum.
You can get a n idea of how more complex the things are if you look for example here, where you can see the variation of the attenuation in water for electromagnetic waves. It does not have radio waves included but I hope you can get some idea.
The visible spectrum is located in that deep valley corresponding to a very low attenuation.