It sucks that 4 other people were killed by the CEOs own hubris. But at least they don't appear to have suffocated to death. At that depth, it would have been instantaneous.
Yeah, that was my concern when we got reports of regular banging noises.
Wonder what made the banging noises...?

The phrase "red herring" originated because the u.s. navy mistook fish noises for incredibly stealthy russia submarines for years :P

Could be anything

"Red herring" as a term originates from the early 1800s. Although you're absolutely right on the larger point; the ocean is noisy and sound carries, there's no telling what it was.
World Wide Words: The Lure of the Red Herring

The origin is finally discovered of the odd English idiom 'red herring'.

World Wide Words