What was a trim party?

At some point, soon after the young diving officer mastered neutral trim, the crew conducted a “trim party”. As he should be, the young officer was focused on the planes, the planes operators and the depth gauge. At some point, he noticed that the boat was suddenly heavy forward. He wasn’t aware of any changes. Since it didn’t resolve itself, he moved water from forward trim to aft. Then, a bit later, he would find that the boat was heavy aft. He still didn’t know the cause. After a while he moved water from after trim to forward. After another little while, the boat was heavy forward again.

This would repeat, heavy forward and then aft, until the diving officer turned around and saw the ten big sailors going toward the forward torpedo room and then to the after torpedo room. That was the trim party. It was, and remains, a submarine institution. It accomplished two important objectives. First, it deflated the ego of the young diving officer. More importantly, it was an object lesson about changes in the weight of the boat. For example, if the captain fired all six torpedoes forward, that was about 19,000 pounds ejected from the boat. The water in the tubes helped offset some of that weight. The torpedomen could help by allowing more water into the drain tanks. But the diving officer still had to react quickly to keep the boat from broaching.

We are told that trim parties continue to this day, although computerized controls may have removed most of the harassment value. Since many diving officers today are chiefs, they likely figure out what’s happening sooner.