They mentioned in the press conference that it was very unlikely that the implosion would have happened after more listening equipment was in use on the scene. I believe there were sonar buoys dropped on Monday, so the implosion likely happened before then.

> it would have been very likely to be registered by at least the controlling ship due to the noise

Why would they be listening? They would be looking at a device that was communicating via SMS or some radar screen at best.

> and that the banging heard afterwards was the implosion

Every 30 min?

Sounds fun. If I was driving a nuclear sub in the Atlantic sea, I'd definitely find an excuse to pop over and play with the kids splashing in my pond.

> Explains why there was no implosion noise originally,

We don't know that. There's a chance a noise was recorded but it wasn't made public in order not to compromise rescue attempts.

It turns out that it’s exactly what happened.

Yes - according to the WSJ and an anonymous US official: https://www.wsj.com/articles/u-s-navy-detected-titan-sub-imp...

There’s a series of episodes of Smarter Everyday where the host goes on a US nuclear submarine and interviews the crew and shows some of the equipment. In one of the episodes, they talk to navigators, who explain that submarines can be invisible to sensors in certain locations because the ocean water is not uniform. Temperature, currents and salinity vary, so a sound could be attenuated in some directions.