[trog]

The USN might also say they knew, without actually knowing, just to exaggerate the claims of their capabilities.

I take everything any country says about stuff like this with massive grains of salt - if they're not providing the information in real-time and then it later turns out to be true then coming back later and saying "oh we knew that all along" is kinda hard to take seriously.

[psychphysic]

That's a good point actually.

Similarly they claim the implosion was detected and triangulated but the banging went undetected until sonar buoys were deployed.