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Surface drones are no longer prototypes confined to coastal trials. In September 2025, the Exail Group's DriX O-16 maritime drone covered almost 1100 miles between La Ciotat and Portugal's Troia peninsula to join NATO's REPMUS naval exercises. This six-day navigation was largely autonomous, including passage through the Strait of Gibraltar, one of the world's busiest shipping lanes.
This technological demonstration raises a very concrete question for boaters. How should they behave when faced with a surface drone underway? And above all, what rules of priority apply between a manned boat and an autonomous vessel?
A surface drone is still legally a vessel
First important rule. A surface drone is not considered a floating object or robot independent of maritime regulations. In most cases, these devices fall into the category of ships within the meaning of RIPAM, the International Regulations for Preventing Collisions at Sea. This text, adopted by the International Maritime Organization, defines the rules of priority and conduct for all ships. In other words, even without a crew on board, a surface drone must comply with navigation rules just like any other vessel.
In the case of the DriX O-16, with a length of around 16 meters and a displacement of around 10.5 tons, it has all the characteristics of a small workboat. It has a hybrid propulsion system, a long range and a set of sensors for detecting maritime traffic.
Supervision remains assured from a remote control center, located here in La Ciotat.
Priority rules remain those of RIPAM
For a yachtsman, the presence of a drone does not change the fundamental principles of navigation. Priority rules remain those defined by the RIPAM.
For example:
- A sailboat has priority over a mechanically propelled vessel.
- A vessel overtaking another must move aside.
- Two mechanically propelled ships passing each other must alter course to starboard to pass port-to-port.
In theory, a surface drone should apply the same rules, thanks to its sensors and navigation algorithms.
Onboard systems typically use a combination of radar, LIDAR, optical cameras and AIS to identify surrounding vessels and calculate an avoidance trajectory.
Drones to avoid maritime traffic
During its crossing between France and Portugal, the DriX O-16 demonstrated just this capability. The drone navigated autonomously for six days, detecting and avoiding maritime traffic. The passage through the Strait of Gibraltar was a particularly demanding test. Hundreds of merchant ships pass through this area every day.
The drone is equipped with a frontal sonar for obstacle detection, a LIDAR system and other sensors that feed its autonomous navigation system. These data enable the drone to follow priority rules while adapting its trajectory.
A challenge for boaters: identifying the drone
In practice, the main difficulty for yachtsmen is identifying these special vessels: some surface drones look like small, fast boats. Others take on very different shapes, with a central hull and an underwater gondola to stabilize the whole and carry the sensors.
The DriX O-16, for example, is almost 15.75 m long and can carry up to 2.5 tons of hydrographic equipment. In particular, it can carry multibeam sonars, towed sonars or acoustic positioning sensors. For a yachtsman, the most important thing is to observe its behavior. An autonomous drone can change its trajectory very regularly, or follow a very stable course.
Caution remains the best rule
Even though surface drones are subject to RIPAM rules, caution is still essential: a drone may be on a scientific, hydrographic or surveillance mission. In some cases, it can tow a sonar or underwater sensor several dozen meters. Getting too close to this type of craft can therefore present a risk. In navigation, the rule remains simple. If you identify a surface drone, it's best to keep a safe distance and avoid cutting off its trajectory.
Maritime drones are developing rapidly. The first 8-meter DriX model, launched in 2017, is now used in 19 countries for seabed mapping, maritime surveillance or scientific research missions. In total, the fleet of these drones has already accumulated over 100,000 hours of operation and nearly a million nautical miles covered.
With the O-16 model, capable of covering more than 2,500 nautical miles at 8 knots, these systems now enter a new category of autonomous vessels capable of long crossings. For yachtsmen, this means they will have to reckon with these new players in navigation. And learn to share the sea with boats... with no visible crew.
