This paper proposes a method to provide depth information about water hazards for ground vehicles. We can estimate underwater depth even with a moving mono camera. Besides the physical principles of refraction, the method is based on the theory of multiple-view geometry and basic point cloud processing techniques. We use the information gathered from the surroundings of the hazard to simplify underwater shape estimation. We detect water hazards, estimate its surface and calculate real depth of underwater shape based on matched points using refraction principle. Our pipeline was tested on real-life experiments, on-board cameras and a detailed evaluation of the measurements is presented in the paper.