How did they get exercise when on a submarine?

On the WW2 boats, it was often claimed that the only exercise the men got was jumping to conclusions or harassing each other. The fact was that there wasn’t the room, and often not the time, for regular exercise. There was usually some work going on during the day in the few compartments with space. As a result, the only real exercise would come from whatever manual work the men had to do or going up and down ladders.