What ? I take offense, Jake, I`ve been asleep most of today already.
I suppose you`re right, if there was something that worked reliably, they would be using it.

"B) There's some theory that sonar signals are unhealthy to some organizms in the sea."
More unhealthy than a daggerboard in the back of the head at 30 knots ? .
Everything man does has an impact on the environment, and we only ever learn from hindsight, which is a wonderful way of saying "oops, sorry", but going ahead and doing it anyway.
Think of all those poor plankton that got shoved out of the way by these mega-cats. WHo knows if they survived the impact.