Yeah I can definitely see a situation where they heard something. It was recorded, and then someone put the pieces together. What I doubt happened was the Navy heard something, then concluded that the something they heard was 5 deep ocean tourists dying in a rapid compression event. Then proceeded to keep their mouth shut while the Coast Guard fruitlessly looked for the vessel.

Maybe there was something the Navy could have done more to prevent the search from running for many days. But they had to err on the side of caution. Imagine a world where they said the sub imploded, the Coast Guard gave up looking. Then years later someone found the sub fully intact sitting at the bottom of the ocean. Not a good thing to have on your conscious.