Maybe. Sound travels longer distances in water than in air, but there still is a limit. And hydrophone chains and buoys are probably not dense enough to hear ev

Maybe. Sound travels longer distances in water than in air, but there still is a limit. And hydrophone chains and buoys are probably not dense enough to hear everything. Volume is also an issue, the Titan is far smaller than a military sub, so the sonar spike corresponding to the implosion will be shorter and of a smaller amplitude. The sonar on their surface vessel should have picked up the noise, if they have one that does recordings and passive mode. But I guess they were too cheap for that as well, since no regular sonar surveilance of the sub is mentioned in the press.