Autonomous Guidance and Navigation (AGN) with intelligent decision making capabili-ties will be an important part of future ocean navigation. This paper is focused on an overview of the AGN systems with respect to the collision avoidance in ocean navigation. In addition, a case study of a fuzzy logic based decision making process accordance with the International Maritime Organization (IMO) Convention on the International Regulations for Preventing Collisions at Sea (COLREGs) will be illustrated.