And that post is followed by one from Mesoman stating that this might apply to low frequency sound waves (as per whale talk) but not to a 37.5kHz signal that is very rapidly attenuated by distance.
It stretches the bounds of credibility a tad that, in all that water, the Chinese just happened to launch a zodiac in the right place to pick up the signal with a surface hydrophone. Either its an anomaly or they were party to some intelligence unavailable to others.