At present, the number of ships under construction, repairing and upgrading, has increased and, accordingly, their marine outputs, which occur when there is an increased number of participants on board, which significantly impairs the habitability of the ship. In such cases, the dynamics of adaptation reactions of sailors to the conditions of navigation may differ from that on active ships and to a greater extent depend on the initial adaptation potential of the organism. This provision was the main hypothesis of the study performed. The purpose of the work is a comparative assessment of urgent adaptation of marine specialists of construction and active ships at marine outputs. Materials and methods. The control groups of 2 crews under construction ships (19 people) and 4 crews of active ships (36 people) were examined using a specially developed complex of clinical, physiological and psycho-physiological methods. The groups of seamen were divided into subgroups depending on the initial adaptation potential of the organism. Studies were conducted — in the pre-shipping period (1st stage); twice during the period of sailing — after 7 days from the moment of going to sea (2nd stage) and 3 days before the end of the voyage (3rd stage); and 4–6 days after returning to the base (4th stage). The results of research have shown the process of urgent adaptation among sailors of ships under construction, when going out to sea, is much more stressful and difficult than a similar process in the crews of operating ships. In addition, difficulties in adapting to the conditions of navigation are largely determined by the level of the initial adaptation potential of the organism, which can serve as a prognostic criterion for unacceptable deterioration in the working capacity of marine specialists. In this regard, it is extremely important not only to revise the existing labor regimes of the crews of ships under construction, repair and upgrade, but also to improve the measures of their medical (including physiological and psychophysiological) support.