Only two effects have a chance to cause a ship to flood:
A ribbon is awarded when a flood is caused to an enemy ship. Though captains may be awarded multiple flooding ribbons, it is not possible for a ship to suffer from the effects of multiple floods; either a ship is flooding or it is not. This is distinctly different from fires, where a ship can suffer from multiple simultaneous fires that stack their damage-over-time effects together.
The probability of a ship flooding depends on where it is struck by the torpedo (or rammed by the enemy ship), the presence of upgrades on the damaged ship (specifically, Damage Control System Modification 1), and the signals mounted on the attacking ship: Juliet Whiskey Unaone () increases the chance of causing a flood by 15%; Victor Lima () increases it by 4%. All the ships except Destroyers have torpedo protection for their citadel. Thanks to this, The chance of flooding and damage are reduced even if the ship doesn't have "Torpedo Protection" in the port UI.
Because destroyers' citadel receive 33% of listed damage from a penetration by default, the torpedo protection is ignored to prevent excessive low damage. Hence Damage Control Modification 1 on a destroyer will not work properly.
In order to calculate the flood chance of a given torpedo versus a given ship, the following formula is utilized:
- The value of "Torpedo Protection" in the port screen is calculated by ROUND[ 1 - ( flood coefficient x 3 ) ].
- The value of "Damage Control Modification 1" is 0.97 if the appropriate upgrade is installed; otherwise, it is 1.
- Damage received from a torpedo is also decreased accordingly to the flood coefficient.
- "Torpedo Flood Chance" and "Flood Protection Coefficient"; the values can be found in the tables below.
- "Signals" varies depending on which signals are equipped; both Victor Lima () and Juliet Whiskey Unaone () can increase the flooding chance of torpedoes.
It is noteworthy that this formula is dependent upon the torpedo striking the torpedo protection (torpedo bulges) on the ship in question. If the torpedo strikes farther forward or astern of this protection, the damage and flood chance reduction afforded by the torpedo protection will not apply.
Flood Protection Coefficient
Ship-Launched Torpedo Data
Aerial Torpedo Data
As an example, we can compare the flood chance of a Type 93 mod. 3 torpedo from Shimakaze against Yamato’s vaunted torpedo protection. The Yamato has Damage Control Modification 1 installed. The Shimakaze commander is flying both the Victor Lima () and Juliet Whiskey Unaone () signals. The flood chance would be:
( 0.15 x 0.97 ) x [ (4.06) + (0.15) + (0.04) ] = 61.84% flood chance
If the Shimakaze was to de-mount the signal flags, the flood chance would be:
( 0.15 x 0.97 ) x [ 4.06 ] = 59.07% flood chance
If the same Shimakaze was to attack a Montana that did not have Damage Control Modification 1 installed, the flood chance would be:
( 0.21 x 1 ) x [ 4.06 ] = 85.26% flood chance
Aircraft carriers, destroyers, and cruisers take 0.25% hit points of damage per second per flood; Kronshtadt, Stalingrad, all battleships take 0.5% hit points of damage per second per flood; and Admiral Graf Spee takes 0.365% hit points of damage per second per flood.
In addition, ships that are flooding have their top speed reduced by 30% at full speed forward, and 60% and at reverse.
The effects of flooding can only be removed by utilization of the Damage Control Party () consumable, or by waiting for the flood duration timer to expire. There are two sections of the ship that can take floods, the aft-ends and fore-ends of a ship. Flooding has a base duration of 30 seconds for carriers, and 40 seconds for the other classes, which can be reduced several ways:
- Equipping Damage Control Modification 2 will reduce the duration by 15%.
- Using a commander with the Level 3 commander skill Basics of Survivability will reduce the duration by 15%.
- Flying the Juliet Yankee Bissotwo signal () will reduce the duration by 20%.
Each of these effects stacks with the others; however, they are multiplicative rather than cumulative.
For example, if all three effects are stacked, the flooding duration is: 40 seconds x 0.85 x 0.85 x 0.80 = 23.12 seconds.
All damage sustained by flooding is 100% recoverable by ships that can use the Repair Party () consumable.
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