A liquid cargo carrying maritime vessel including a plurality of liquid cargo carrying tanks and a plurality of gas expansion trunks wherein each gas expansion trunk is above, associated with, and in fluid communication with a respective tank therebelow, via slotted apertures in the deck. Each gas expansion trunk is fixedly positioned on a portion of a deck of the vessel above the associated tank and in fluid/tight relationship with the deck over a periphery of the trunk which encloses the totality of slotted apertures in the deck. Depending on the attributes of the ship, the expansion trunk is preferably located directly above the tank and at the highest point available of the tank and as far forward on the tank as possible. Alternatively, and depending upon obstructive constraints and vessel conditions, the trunk may be placed in other locations such as aftmost on the tank or inbetween. Gas expansion trunks are suitable for being retrofitted onto existing ships or integrated into the configuration of new ships.