Liquid bulk carriers carry unpackaged, liquid, cargoes. While a subset of bulk carriers, the term 'bulk carrier' usually implies 'dry bulk carriers' exclusively. Liquid bulk carrier variants:
Gas cargoes are liquefied to reduce explosiveness and increase capacity, at the expense of refrigeration units and pressure vessels. These pressure vessels are often aluminum to reduce weight, spherical, and only superficially attached to the hull structure (they are not structural members of the ship), allowing the vessel to flex & bend without themselves rupturing.