In the same way, if the impulse reflects on the bottom of the sea, there is an area that is estimated as equal to 15% of the distance between the bottom and the profiler where measurements cannot be made as the intensity of the reflected pulse masks the lowest echo intensities from areas close to the bottom. This phenomenon can also be observed if the profiler is placed on the bottom, pointing towards the surface. The reflections on the surface can mask echoes from layers that are close by.