Industry insiders said pre-dive preparations would, or should, have included checks on the submersible’s structure and all of the vessel’s mechanical and electrical systems. These would have been absolutely crucial given the crushing pressure generated at 3,800 metres below sea level – the depth of water the Titanic came to rest in – and the real potential of getting lost: the site is nearly 400 miles off the coast of Newfoundland. What checks were performed before the submersible and its five occupants slipped beneath the waves are unclear, but standard checks and procedures were followed, the Guardian understands.