Yes, I've lost a few boats to critical flooding. Whether or not you're in danger from flooding depends on the extent of it versus how fast its being pumped out, how fast you're sinking, your depth, and lastly the condition of your hull.
If you're not running silently whenever you get flooding you'll see two numbers in the compartment: one is how long til the compartment completely floods and the second is how fast its being pumped out. One completely flooded compartment can sink your boat, and multiple flooding compartments can have the same effect even if they don't flood completely.
The condition of your hull affects crush depth and lessens your margin for getting flooding under control. For instance, in one campaign my boat broke apart at only 40 meters because the hull was at 16% integrety after being shelled and rammed by a destroyer.
With all that said, if your hull isn't in bad shape, your not too deep, and you're not sinking, then you can ignore minor flooding until repairs won't compromise your stealth or until you're forced to deal with it.
|