Tanker provided with swash type bulkheads

A tanker comprising a cargo tank, at least one bulk head subdividing said cargo tank into at least two compartments, said compartments being at least half full of a liquid cargo having a specific gravity less than water, said compartments being closed liquid tight from top to bottom except for at least one permanently open hole at the bottom of the compartments through which said compartments permanently communicate with each other, the level of said liquid in the compartments being spaced above the highest point of said at least one hole by a distance equal to at least half the height of the compartments.