Yes they do travel through water. Their attenuation is frequency dependent and is given by the skin depth of water. Lower frequency waves propagate further than high frequency. At the wireless frequencies, water highly attenuates its propagation such that it can only communicate a few meters, but submarine ELF frequencies (73 Hz) can penetrate on the order of 1 km with only 60 dB loss or so, and ionospheric waves (approx .5 Hz) go through the complete ocean and into the lithosphere. [Source: Me. I am currently doing heavy research into this subject for a research contract] As a layman thinking only of WANs and 2.4 GHz stuff I could see how you could make this mistake, but what you way is false. Even GHz waves will travel, albeit an insignificant amount, but still finite.