If this plane hit the ocean, our undersea sonic sound systems or our subs would have picked it up. The sound would have been akin to an explosion, underwater.
A ship hitting the waves would be a repetitive sound that would be recognized for what it is.
A one time impact of the size of this plane crashing in an area where there would not be other such sounds would be an anomaly.
The sonar operator, or those who “listen” on the underwater sound system would go “What the heck was THAT?”.
How many recorded songs can your phone hold?
Well subs have a data bank of millions of recorded sound anomalies and with a visual graph, from tonal hertz electric motors to damaged propeller signatures, mating biological and tectonic plate activity, they most certainly have a library of explosive sounds, especially stuff that collapses underwater from pressure. Part of the cat and mouse game carryover from the cold war was being a hole in the water and listening for tonals. Boomers especially.