Abstract: Passive detection and localization of objects in the water environment is a desirable undertaking not only from the point of view of underwater defense technology but it is also associated with the military aspect of security, especially in respect to the protection of narrow passages. waterlines and ports. Observation of a specific region of the sea area, besides the technical means (hardware) that allow the data acquisition, requires also the application of a specific algorithm for the determination of ship's localization (software). This article presents the possibilities of ship's detection basing on the analysis of acoustic, magnetic, electric and pressure fields.