Subaquatic investigation technicians are trained to examine crime scenes underwater, often in lakes or rivers. These experts rely on technology like remotely operated vehicles (ROVs), which are underwater drones controlled from the surface. ROVs can operate for much longer periods than divers, making them valuable tools for exploring submerged environments. In September 2022, an old Cessna 152 airplane was intentionally submerged in Lake Saint-Cassien in the Var region of France. The purpose was to test how an ROV could assist in a real underwater crime scene investigation. This experiment was evaluated in July 2026 to assess the effectiveness of ROVs in such scenarios. One of the ROVs tested was the Victor 300, a prototype developed specifically for underwater investigations. This device is connected to the surface via a cable that sends control signals and transmits real-time data. It is equipped with a high-definition camera, a stereoscopic vision system for creating 3D images, a multi-beam sonar, and lighting to navigate dark or murky waters. The Victor 300 was built using open-source software and components from the American company Blue Robotics, with special modifications to its motor layout. This allows the ROV to maneuver more effectively in challenging underwater conditions. In France, the National Gendarmerie has been training subaquatic investigation technicians since 1962. The National Naval Training Center of the National Gendarmerie (CNING) in Antibes is a key institution for this training, working closely with the National Gendarmerie Criminal Research Institute (IRCGN) to develop techniques tailored for underwater environments. Piloting an ROV is considered an additional skill for these technicians, who are responsible for analyzing scenes, planning search strategies, and preparing for the use of divers when necessary. The Saint-Cassien experiment aimed to explore how an ROV could investigate a submerged scene without disturbing it. Victor 300 had to move carefully, avoid resuspending sediment, and illuminate the area without causing glare. The drone’s thrusters could disrupt the water, and its cable could get caught on the plane or the lakebed. Any accidental contact could displace evidence before it was noticed. Before any object was collected, its location, depth, and orientation had to be precisely documented. Using an ROV enhances the ability to explore underwater scenes. With an autonomy five to ten times greater than a diver, the ROV can observe the scene for longer periods, record multiple images, and revisit points of interest without risking human exposure. This allows divers to focus on tasks that require direct involvement, such as collecting evidence or making delicate manipulations. The ROV also helps preserve evidence by allowing investigators to observe a scene before making physical contact, preparing human teams more effectively and saving time in the overall investigation. Underwater photogrammetry allows investigators to create 3D reconstructions of a scene using images taken from different angles. This technique is included in the Victor 300, but divers still have advantages in terms of immediate perception, mobility, and ability to adjust lighting and framing. The ROV's pilot is limited by the camera’s field of view, the cable’s movement, and the drone’s propellers, which can stir up sediment. However, in situations where a diver cannot be deployed due to dangerous conditions, the images captured by the ROV remain invaluable. The multi-beam sonar on Victor 300 is especially useful in very murky water, where visibility is limited or nonexistent. It uses sound waves to detect shapes, measure distances, and map the underwater terrain. While it does not replace visual images, it complements them by revealing features that are invisible to the camera and guiding the ROV to areas that need closer inspection. The Saint-Cassien experiment highlighted that technology is only effective when it respects the integrity of the scene. Underwater, everything moves more slowly, and conditions are more unpredictable. The ROV does not replace human judgment but provides an additional perspective, more observation time, and better documentation. In this way, underwater drones can enhance investigations by supporting human expertise rather than replacing it.