The evolution of Underwater Vehicles (UVs) over recent decades has transformed them from experimental models to indispensable tools, reshaping the landscape of ocean exploration. This book will explore the current state-of-the-art trends, emerging technologies, and potential deployment scenarios in the field of UVs. Technological advancements in propulsion, navigation, sensing, and materials have facilitated the development of sophisticated underwater platforms capable of autonomous operation, improved maneuverability, and extended mission endurance. From remotely operated vehicles (ROVs) to autonomous underwater vehicles (AUVs) and hybrid systems, a diverse spectrum of platforms now caters to scientific, commercial, and defense needs. The discussion will delve into challenges and opportunities associated with deploying these advanced underwater vehicles in complex environments, including deep-sea exploration, harsh marine conditions, and confined underwater spaces. Furthermore, it will evaluate the impact of artificial intelligence, machine learning, and swarm robotics in enhancing the autonomy and collaborative capabilities of these vehicles for efficient data collection and decision-making processes. This book will not only serve as a foundational guide but will also provide practical insights into the cutting-edge applications of these vehicles, showcasing their versatile roles as forefront entities in underwater technology.