The lack of alien t.v. broadcasts makes me suspect it takes a lot more than a rocky water world. Seriously, our planet must look insane in the radio spectrum right now...if anyone is out there to see it.
If you realize the distance involved, then lack of "alien TV broadcasts" makes all the more sense. After all, our broadcasts (Radio and TV) have only traveled around 100 light years. Our galaxy is 100,000 light years across. At this point, our first transmissions in the radio spectrum (Hitler's Reichstag address being the loudest, ironically) have traveled past about 113,000 stars, in our local neighborhood.
The Drake Equation puts the probability of life at "around" one in one billion star systems. (though it could obviously be much higher or lower, this is just a starting block)
As well, it should be noted, in that small time, ~100 years, we've gained the possibility of exterminating ourselves. Our development should be considered average until proven otherwise. Therefore, many intelligent species, by probability, will have wiped themselves out shortly after becoming a "radio/TV emanating race"
Also, we've only been listening, and listening is a "loosely" used word, for about 20 years. That means only the stars within 20 light years have been "checked" for signals. In all honesty, we'll probably never hear anything from "out there" unless it's specifically meant for us to hear. The distance is much too great, and time much too short.
