This all refers back to the loss we have allowed in underwater acoustics capabilities. Before 1991 we could detect, localize, and track a Soviet nuke and make repeated passive attacks without their ever knowing we were there. Since then we have let our ASW capabilities shrivel to the point where the new P-8* is reportedly incapable of doing electronic ASW at all. We went from 451 mission-ready P-3s in the 80s to just 80 or so airworthy now. You may not see the connection between ASW and finding a submerged sound source, but they are the same.
* If we build the P-8 in any quantity
...and half of those 451 mission-ready P-3s flew over my house every day in the 80s heading from Moffett NAS to the Pacific on ASW missions. Windows rattled, the chandelier swung...what a racket. All gone now. The degradation of our capabilities is frightening.