The possibility of using the ecologically safe operation on a closed-loop circuit instead of an open-loop cooling system is considered. For this purpose, it was proposed to use the ballast tanks on the ship. To ensure effective heat removal, it is proposed to apply a jet inlet of coolant to the hull shell of a ship. The flow regimes of the impact fluid jet were visualized. The critical Reynolds number is determined. Heat transfer coefficients and generalizing calculation dependences are determined by experiments.