Water is actually very good at blocking radio waves. I don't have exact numbers but pretty sure nothing can transmit from as low as a few tens of feet.
even if that's the case, then the final "message" upon impact/underwater limits would have been transmitted from a specific location.
Perhaps that would even be accurate within a 5 mile radius with the Indian Ocean.
Had they known that from Day One, then even if it took 24 hours to get helicoptors there,
perhaps there would be survivors, or at least un-sunk wreckage.
Which bring us to the next point:
Why can we practically see the make and model info of our cars from Google Earth space satellites, but not what's on the ocean's surface!?