Unmanned Underwater Vehicles (UUVs) have emerged as vital tools in modern maritime operations, enabling safe, efficient, and precise tasks across a variety of underwater environments. This review aims to present a comprehensive examination of the current state, technological foundations, and emerging developments in UUV systems. It explores the key enabling technologies including propulsion mechanisms, energy storage and management, underwater communication protocols, sensor integration, and advanced navigation and control systems. The analysis draws attention to both Autonomous Underwater Vehicles (AUVs) and Remotely Operated Vehicles (ROVs), highlighting their respective operational capabilities and domains of use. Applications of UUVs are broad and impactful, spanning from naval defense, surveillance, and mine countermeasures to oceanographic research, undersea infrastructure inspection, and environmental monitoring. With increasing integration of artificial intelligence and machine learning, these vehicles are evolving into intelligent systems capable of performing complex missions autonomously. However, several persistent challenges hinder the full operational potential of UUVs. These include limitations in power supply, difficulties in underwater communication, navigation in GPS-denied environments, and resilience against high-pressure and corrosive underwater conditions. This review further outlines the future direction of UUV research, emphasizing the importance of interdisciplinary approaches, bio-inspired design, swarm robotics, and enhanced autonomy. The findings provide valuable insights for academics, engineers, and stakeholders aiming to advance the field of underwater robotics through innovative and sustainable solutions.

Keywords: Unmanned Underwater Vehicle (UUV), Autonomous Underwater Vehicle (AUV), Underwater Communication, Marine Robotics, Navigation and Control Systems, Subsea Applications