Orrr, maybe to fuck with the sub's mind a but more, how about just making a beep or buzzer sound every so often as time goes by? But not something simple and uniform like every 5 minutes. Maybe something more like every 2 minutes and 34 seconds, the sub hears a beep. So he's kind of informed how much time has gone by, but good luck concentrating on that and remembering how many beeps he's heard, and multiplying it by some crazy amount of time like that. I imagine it would probably just motivate him to move faster regardless, because it's almost hopeless trying to figure out how much time has passed with any level of confidence that he's correct in his math. *evil grin!* What do you think of that idea? Anything to add or tweak?