Abstract: The integrated tug-barge vessel consists of a separable barge and tug; the stern of the barge is formed of a pair of rearwardly extending projections defining a notch therebetween; the inside wall of each stern projection displays a buttress that engages into a longitudinal guideway, defined by a pair of rails on each sidewall of the tug, when the tug approaches the stern notch of the barge; the engagement of this buttress into a constricted portion of the guideway controls the vertical and torsional movements of the tug as it engages the stern of the barge; the disclosure herein is also concerned with describing a coupling device for snugly linking the tug to the barge; it includes a housing located at the stern of the barge and a linkage assembly mounted at the bow of the tug consisting of an hydraulic cylinder that actuates an arm and lever arrangement for the engagement and the disengagement of the tug to and from the barge.