Asimov wrote:

Hi,

I was thinking about why radio wave communications are not generally
used underwater. Basically I'm asking what are the quantitative
components of the underwater medium that makes it impractical except
for perhaps very short ranges. Things like attenuation, impedance,
etc... Does any one here know these details or have them handy?

A*s*i*m*o*v

... Acme Corp: Unlimited credit for disadvantaged coyotes.

The conductivity of water causes great attenuation at all but very low
frequencies. Think "skin effect".

That having been said, the US Navy (and probably all other folks with
subs) use extremely low frequency RF (30kHz IIRC) to communicate with
strategic nuclear subs.

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com