Reg Edwards wrote:
The permittivity, K, of water is about 80.

The relative velocity of propagation along a wire immersed in water is
about VF = 1/Sqrt( K ) = 0.11
. . .

When the material is conductive, like salt water, you also have to
consider the conductivity in determining velocity factor. The velocity
factor in salt water is 0.0128 at 7.5 MHz, 0.0175 at 14 MHz (based on
conductivity of 5 S/m and dielectric constant of 81).

Incidentally, you can get this information directly from EZNEC,
including the demo program. Select a real ground type, then find the
velocity factor, skin depth, and other information in Utilities/Ground Info.

Roy Lewallen, W7EL