until it had been classified by an independent body. but mr rush responded that he was tired of industry players who try to use a safety argument to stop innovation. we ll have the latest on the search for the vessel, after debris was found on the sea floor. but first, here s our science editor, rerbecca morelle, we already know that experts had issues with the safety of the titan submersible. their worries were over its unusual design, its non spherical shape,?the reliability of the material it was made of carbon fibre ?and the fact it had also not been through any external independent certification or classing process. now the bbc has been exclusively given an email exchange between stockton rush the ceo of oceangate, who died in the incident and a leading underwater exploration specialist, rob maccallum, who has overseen numerous deep sea explorations. in an email sent in 2018, rob maccallum warned stockton rush: