A couple of "good ones" I saw on various mailing lists today…
It reminds me of the midshipman informing his captain that he was going downstairs. To which the captain snapped, "Downstairs is below; that side of the ship is port, and that, starboard. That’s not a floor you’re walking on, but a deck. If there is anymore civilian talk aboard my ship, I’ll throw you through that little round window over there!"
An old shipyard joke about working tolerances:
Engineers work to the nearest thou, platers work to the nearest quarter, carpenters work to the nearest inch and shipwrights work to the nearest ship.