This paper is dealing with the problem of extinguishing fire on ships and off-shore equipment characterized by high degree of danger caused by presence of explosive or life threatening substances. Special device Cold Cut System Cobra combining cutting possibility and production of water mist is presented. Its advantages and application possibilities are discussed. This fire extinguisher has been widely used for more than one decade but based on a literature search we suppose that its potential is not fully exploited in marine applications. In cooperation with fire-fighting rescue station in Silesian Ostrava laboratory measurement of reaction forces of Cobra slurry jet was realized at the Technical University of Ostrava. It was discovered that measured force was about 120 – 150 N therefore it represented approximately one third of the theoretical maximum value. The measured force appeared to change not only with the type of material but also with the thickness of the layer being cut, but the change was not significant from the point of view of handling the lance during intervention. Our research may deepen firefighter’s knowledge of the tool they are working with and therefore improve safety of their work.