Autonomous Underwater Vehicles (AUVs) are vehicles that are primarily used to accomplish oceanographic research data collection and auxiliary offshore tasks. At the present time, they are usually powered by lithium-ion secondary batteries, which have insufficient specific energies. In order for this technology to achieve a mature state, increased endurance is required. Fuel cell power systems have been identified as an effective means to achieve this endurance but no implementation in a commercial device has yet been realized. This paper summarizes the current state of development of the technology in this field of research. First, the most adequate type of fuel cell for this application is discussed. The prototypes and design concepts of AUVs powered by fuel cells which have been developed in the last few years are described. Possible commercial and experimental fuel cell stack options are analyzed, examining solutions adopted in the analogous aerial vehicle applications, as well as the underwater ones, to see if integration in an AUV is feasible. Current solutions in oxygen and hydrogen storage systems are overviewed and energy density is objectively compared between battery power systems and fuel cell power systems for AUVs. A couple of system configuration solutions are described including the necessary lithium-ion battery hybrid system. Finally, some closing remarks on the future of this technology are given.

The aim of the work is to evaluate various designs in order to arrive at some guidelines for choosing a good standard design by means of a fatigue damage analysis in the connection between longitudinal stiffener and transverse web frame on container ship side-shell structure located in the upper wing torsional box. Design proposals and recommendations are developed, based on numerical and experimental analysis, which allow, from different structural configurations formed by combinations between cut-outs and collar plates, to establish more and less adequate structural designs in one of the ships with the greatest future projection. In the first phase, the cut-out without influence of the longitudinal stiffener is studied and the stress state and fatigue assessment are determined. In the second phase, the longitudinal stiffener is taken into account under the presence of the collar plate in the model and different geometrical alternatives (thickness, ducktail, overlap and radius of curvature) and their influence on the determination of stress and fatigue life are studied. From the different configurations, the most appropriate combination is established and structural solutions are proposed in order to improve the design.

The increasing demand for reliability and safety in naval and offshore structures has accelerated the adoption of advanced Structural Health Monitoring (SHM) techniques. Among them, acoustic methods—ranging from passive acoustic emission monitoring to guided ultrasonic waves—have demonstrated exceptional potential for early detection, localization, and characterization of structural damage under harsh marine environments. This review provides a comprehensive and critical synthesis of the state-of-the-art in acoustic-based SHM applied to ships, submarines, offshore platforms, and floating renewable energy systems. Special emphasis is placed on the comparative performance of different acoustic techniques, their integration with numerical modeling and data-driven methods, and their suitability for real-world deployment considering hydrodynamic, operational, and environmental constraints. By bridging current achievements with future challenges, the paper highlights research gaps and outlines key directions to accelerate the transition of acoustic SHM technologies from laboratory studies to widespread industrial applications. This review aspires to serve as a reference work for both academic researchers and practitioners, consolidating knowledge and inspiring innovation in the field.