Preventive Maintenance
Given that a submarine is essentially a large, intricate machine, it’s not surprising that they require significant upkeep. For this reason, sailors often have to work long hours making sure every hatch and valve is in proper working order.
The maintenance of the electronic equipment and launch tubes is also part of this. This work, in fact, takes away from the crew’s leisure time. Even when they are not on duty, the sailors get a little rest, it appears.