A phrase of Navy jargon
used by submarine
rs to describe a sub
when it is not moving and is rigged for silent running
This means that there is nothing running on the boat that is not needed. Laundry, ventilation, galley, showers, everything is turned off (except the coffee maker when operating under silent running for long periods of time). The crew wears soft-sole shoes or padded shoe covers. Pretty much the only things on are the reactor and coolant pumps. Remember the shaft is not turning because the boat is stopped. Many times the captain will bottom the boat to avoid active sonar detection.