I had an issue recently relating to moonpools on large ships, specifically that a moonpool was a source for a constant oil spill leaking into the area surrounding my ship. After some testing I believe I have found the cause of the issue, though I am not exactly sure why it happens.

At first I had thought I had some leak in a different area of my ship. After looking over every corner of the ship about 8 times and not finding a leak, I had decided to cover the bottom of the moonpool. To my surprise, this solution worked and the oil spilled had stopped for the entirety of a 10 minute trip to a neighboring island.

When investigating what it could be, I had decided to start removing everything in the room one by one. After a few tests I had found that the air filters used for pressurizing and depressurizing the rooms had been the culprit.

The setup had originally been this: four electric pumps pumping from four huge gas tanks set to contain 100% air directly into the room via air filters to pressurize the room, and four electric pumps pumping air from the room back into the huge gas tanks via air filters to depressurize the room and fill it with water.

	Removing the system and opting to pump the air directly in and out of the room instead of the ship's HVAC system did the trick, and oil stopped leaking into the ocean wherever I went. If I had to guess what the cause of this issue is, I would say that having a pipe and air filter connected to huge gas tanks was somehow spawning oil inside the moonpool when is was submerged. This could possibly be an issue with the huge gas tanks specifically, as an almost identical setup that does not include the huge gas tanks and instead pumped the air in the moonpool in and out of the ship directly seems to have completely solved the problem.