• A catamaran Unmanned Surface Vehicle (USV) with flexible hoses is designed for underwater photography. • The influence of bow shape on speed and stability is investigated through water tank experiments. • The stability characteristics of the USV and underwater camera are evaluated under regular wave conditions. • Field experiments validate the effectiveness of the proposed underwater photography system in real sea conditions. To advance the development of underwater photography technology, we developed a portable catamaran unmanned surface vehicle (USV) tailored for practical applications, originally using inflatable hoses. However, ensuring the stability of photographic equipment on such a compact USV in waves remains a critical challenge. This study first examined the effects of bow shape, where the bows also function as air-sealing caps, on vessel motion in waves through water tank experiments. Additionally, the USV was connected to an underwater camera via a flexible fiber tether, and the oscillation of both the USV and the camera was measured under regular wave conditions. Field tests were finally conducted at Hiratsuka Port to evaluate the operational and underwater imaging performance. The results show that the wedge-shaped bow design balances moving speed and pitch motion of the USV in waves. With the camera installed, surge, sway, and heave motions were examined under stationary conditions, head waves, and following waves. Under stationary conditions, while the sway acceleration of the camera was higher than that of the USV, the surge and heave accelerations of the camera reduced by more than 50%. Under cruising conditions, the surge acceleration was lower in following waves compared to head waves, and vessel control was more challenging in head waves. For practical applications, navigating in following waves after reaching the target location can help capture clearer images and videos. The field experiments demonstrated that underwater photography remained stable with minimal shaking, resulting in clear images suitable for further image analysis.
Li et al. (Wed,) studied this question.