Abstract: A system for geolocation of an object in water includes: first and second devices for immersion in, or to float on, water, the first device including a light source that emits a light beam; the second device includes a camera and a measuring device; and a processing unit, operatively connected to the camera, and configured to: determine a vertical distance between the first and second devices based on the depth of both devices, capture a 2D image of the first device via the camera, calculate the pixel position in the image of the light beam from the light source, calculate a position of the first device relative to the main reference frame based on the pixel position of the light beam, the orientation of the camera, a position of the second device relative to the main reference frame and the vertical distance.