Doppler
For all the intelligent discourse earlier in this thread regarding Doppler effects of electromagnetic waves, the mention of Doppler with respect to sound waves is curiously missing even though the effect is far more pronounced. The odds of getting precisely a 37.5 kHz return in an extremely noisy ocean are pretty low, at any considerable distance from the source.
These underwater sounds that have been heard may be the haystack we are looking for, or they may not. The odds are not in our favor without some kind of verified physical debris in hand. We shouldn't get our hopes up until then.