The subject of autonomy and mission planning have been comprehensively investigated on various frameworks over the past decades. It has been briefly discussed in previews chapters that among attempted scopes of autonomous operations, the underwater exploration remained still restricted to particular tasks with a low-level of autonomy. Underwater robotic platforms arouse more interest and broadly used in maritime approaches to achieve routine and permanent access to the undersea environment. Autonomous underwater operations including high and low-level mission-motion planning for an AUV is targeted as a case study in this book to precisely investigate challenges that a vehicle can face in long-range missions in harsh environment. These classes of autonomous vehicles are largely employed for numerous purposes such as scientific marine exploration, surveys, sampling and monitoring undersea biodiversity, offshore mapping, installations and mining, etc., Sibenac et al in IEEE OCEANS’02 MTS: 2002 , Barrett et al in IEEE Oceans Sydney: 2010 .