[krisoft]

> They do, but not the depths we're talking about

We really don’t know what depth the noise was comming from.

That being said it is vanishingly unlikely that an unrelated submarine trying to remain stealthy would be banging on their hull every half an hour.

[themoonisachees]

Very true, it is a known factoid that submarines sometimes bump into each other because they can't tell that another sub is there. Doing so much noise as to be spotted from aircraft is crazy.

[flaminHotSpeedo]

Strictly speaking I think it was buoys dropped from aircraft, it's not a listening device on the aircraft itself