Even with the break to get out of the bathysphere, Jack's pause is a noticeably long one. The geography is right as far as where he crashed versus where he was going, but Sinclair probably would not have come along as far as he has if he couldn't at least spot a liar, never mind a terrible one. He's a gentleman, though. He'll let it slide.

"Where were you working, son? Maybe I can find something for you to do around here."