In marine environment there are different types of objects, such as ships or naval mines, which should be located and identified. One of the location methods is based on the electric potential distribution measurement [1, 2], The object with an insulating or conductive casing, placed in an electric field, causes some field perturbations. For the purpose of the object location the dimensions of the area, where it is possible to determine electric field perturbations by measurement, are important. In this way one can pre-determine the extent of the system for locating and identifying objects placed in the seawater. This paper presents an analytical approach to the perturbation analysis of electric field distribution caused by a sphere and an ellipsoid placed in a uniform electric field. The distance, beyond which the uniform electric perturbations can be neglected, is determined.