I have no idea if this is "realism"...could a sub not run Silent Running AND maintain depth.
You are basically shutting down your pumps when you run silent effectively decreasing your neutral bouyancy trim as you fill the bilge with water leaks. I keep an eye on that and if I have to run the pumps, I do!
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DID, no cheats, no shortcuts, no non-historic equipment deviations. Boat and crew safety is integral with my immersion style! Follow the historic events during your patrol:
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