Only two effects have a chance to cause a ship to flood:
- Being struck by a torpedo (enemy or friendly).
- Being rammed by an enemy ship.
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 both ships (Juliet Whiskey Unaone increases the chance of causing a flood; Victor Lima increases the chance of receiving one). Many ships — most battleships and aircraft carriers, as well as some heavy cruisers — have torpedo bulges built into their citadel armor that reduces not only damage taken from the torpedo, but the chance that the torpedo will cause flooding.
Flooding damage reduces a ship's health by 0.667% of its total health pool per second. If a flood is not controlled (see below) and is allowed to run for its full duration, a ship will lose just over 60% of its total health pool to a single flood.
In addition, ships that are flooding have their top speed reduced by 15-20% (depending on class).
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. Flooding has a base duration of 90 seconds, 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: 90 seconds x 0.85 x 0.85 x 0.80 = 52.02 seconds.
All damage sustained by flooding is 100% recoverable by ships that can use the Repair Party consumable.