## 1 Introduction  
Bathymetry is the study of the underwater depths of all water bodies, including oceans, rivers, and lakes, based on measuring the distance from the floors to the surfaces of these water bodies [1]. These data generate navigational charts, 3D models, seafloor profiles, information about the marine environment, and shaded relief maps, among other things [2, 3]. In addition, advancements in specialized technology have meant that bathymetric survey equipment can be used to carry out increasingly accurate analyses on a global scale [4, 5].  
These technological advancements have enabled the development of acoustic instruments geared towards bathymetry, such as single-beam [6, 7] and multibeam [8, 9] echo sounders, which require an aircraft or ship for their transportation and operation. However, both echo sounders have advantages and disadvantages in terms of cost, scope, and size [10, 11]. Multibeam echo sounders and laser scanning have been used to conduct surveys both inland and in coastal waters [12, 13]. The comparative advantages of using unmanned aerial vehicles (UAVs) are decisive in terms of the cost and accuracy of underwater measurements [14, 15]. In addition, these vehicles are used because of their potential large-scale mapping and the possibility of accessing remote and restricted places [16, 17]. It is important to note that UAVs are vulnerable to physical capture and node-tampering attacks, so it is advisable to consider security techniques to ensure communication between the UAV and its ground station [18]. The main vulnerabilities of UAVs that can lead to security problems are as follows: sensor tampering and imitation of the GPS signal, drone malware affecting drone control and data, cyber or physical attacks to the UAV's flight controller and ground control station, and the wireless communication network used in the UAV [19]. In the past few years, lidar (light detection and ranging) systems have become more popular in surface mapping as the laser equipment can be mounted on an aircraft (be it a fixed-wing or rotary aircraft). Lidar involves the transmission of laser light using infrared and green wavelengths of the electromagnetic spectrum through the water to calculate seafloor depth and obtain dense data points. This technology can be expensive, but it enables the surveying of an area day and night, with an extension of up to 70 m, depending on the water clarity [2].  
Another method used in aerial mapping is photogrammetry [20; 21]. In recent years, the combination of digital photogrammetry and UAVs has allowed the extraction of 3D geometries from 2D images [22; 23]. This results in point clouds with photorealistic texture, triangulated meshes, DEMs, and orthomosaics. To ensure the quality of the images, it is important to consider both the UAV and camera parameters, e.g., the definition of the aerial extent of the survey, the ground sampling distance (GSD), the distance between the camera and the subject, the focal length, the sensor size, and the pixel size [24; 25]. Compared with lidar technology, photogrammetry with UAVs can be a less expensive method for surveying shallow waters [26]. In addition, photogrammetric flights can help surveyors carry out surveys of more complex areas [27; 28].