An assembly for carrying cargo which comprises a cylindrical tank rotatable about a horizontal axis and having a torque partition member dividing it into an upper and a lower compartment, rotating rails provided around the periphery of the tank, support rails for guiding and supporting the rotating rails, and means for locking the tank against movement. The compartments of the tank are connected to cargo pipes and gas pipes through a connecting means associated with each tank. A liquid cargo can be loaded in the upper compartment simultaneously with the unloading of the liquid cargo from the lower compartment and the loaded upper compartment can be placed in a lower level position by the rotation of the tank caused by a torque produced by the partition member during loading and unloading.