There was something about this on QI with Stephen Fry not long ago.

I'm damn positive that it's got ALOT to do with the water and the frequency.

I highly doubt it could cause damage though, otherwise there would be ships and boats disappearing all the time.

I think, although im not sure, that only other wales can hear it at long distence? Not sure about that one.

Very interesting though - really, it's quite amazing. So many things in this world are. Like how a moron can run England. [Oh, he cant! Nevermind!]