Stacked in pallets on cargo ships, the weight of the top layers simply crushed those below, resulting in fuel losses of up to 40 percent, and making unloading the intact containers extremely hazardous with thousands of gallons of petrol sloshing around in the bilges and the fumes powerful enough to render seamen unconscious, not to mention the danger of fire or explosion.
From:-
https://www.exploringoverland.com/overland-tech-travel/2012/8/17/irreducible-imperfection-the-flimsy.html