He starts sketching one out based on the depth of one hundred and thirty, which seems reasonably close to one hundred and fifty-four. After working on it for about an hour (long enough to imagine all sorts of specious details) he happens to notice that the table he’s been using is in feet , not meters , which means that all of these divers have been going down to a depth that is way more than three times as deep as the maximum that is even talked about on these tables.