## 3 Trends in Operational USVs
### Hull Materials and Main Dimensions  
Concerning the hull materials among USVs, their distribution highlights a clear preference for aluminum and composite materials, with polyethylene also being widely used (Figure 5a). Aluminum is a popular choice due to its lightweight properties, corrosion resistance, and ease of fabrication, making it ideal for both commercial and defense applications. Composite materials, such as fiberglass and carbon fiber, offer high strength-to-weight ratios, reduced maintenance requirements, and excellent durability, which explains their significant presence. Polyethylene, although not as dominant, is favored for smaller USVs due to its cost-effectiveness and impact resistance. Steel, on the other hand, is rarely used in USVs, likely because of its higher weight and maintenance demands due to its susceptibility to corrosion. This distribution reflects the industry's focus on lightweight, durable, and low-maintenance materials that enhance operational performance. Just as material selection reflects operational priorities, USV length also plays a crucial role in defining mission scope and capabilities. The length distribution of USVs reveals that most models are relatively small, concentrated between 3 and 7 m, with significantly fewer models exceeding 10 m (Figure 5b). This trend suggests that the majority of USVs are designed for nearshore and coastal applications, where compact and agile platforms are preferred for tasks such as environmental monitoring, maritime surveillance, and hydrographic surveys. The reduced presence of longer USVs can be attributed to the increased complexity, cost, and logistical challenges associated with deploying and maintaining larger vessels. However, a few models extend beyond 15 m, likely designed for specialized missions such as long-range offshore inspections and military applications. The overall trend indicates that the industry prioritizes compact designs that balance operational versatility, cost-efficiency, and ease of deployment, catering to a broad range of commercial and defense applications. Alongside length, beam dimensions further shape USVs' hydrodynamics, stability, and transportability. The distribution of USV beams suggests that most models have a beam between 1 and 2.5 m, with a peak around 2 m (Figure 5c). This relatively narrow beam range indicates a preference for streamlined designs that enhance hydrodynamic efficiency, maneuverability, and transportability. USVs with beams around 2 m may be looking for a balance between stability and performance, which allows them to operate effectively in various conditions without excessive drag. Wider beams, though less common, are likely found in larger or specialized USVs that require additional transverse stability for  
Figure 4: Annual and cumulative growth of Unmanned Surface Vehicle (USV) models in the market. carrying payloads, such as scientific instruments, communication equipment, or modular sensor systems. On the other hand, very narrow beams, below 1 meter, may be associated with lightweight, high-speed models designed for rapid deployment or reconnaissance. The observed beam distribution reflects design considerations that prioritize efficiency, ease of deployment, and adaptability across diverse maritime environments. Finally, draft distribution provides insight into the intended operational environments of USVs, complementing the trends observed in other design features. The draft distribution of USVs indicates that most models have a shallow draft, typically below 1.25 m, with a significant concentration around 0.75 m (Figure 5d). This trend suggests that USVs are primarily designed for operations in shallow waters, nearshore environments, and inland waterways, where limited draft enhances accessibility and maneuverability. Shallow-draft USVs are well suited for applications such as environmental monitoring, port security, and bathymetry surveys, where deeper hulls could pose operational constraints.