Since 1950s, studies on floating type Nuclear Power Plant (NPP) have been attempted. Recently, Russia’s first floating NPP has been completed and will be operated in 2012. However, the floating type only can mount relatively small size NPP and easily affected by ocean waves or Tsunami. In this study, we adopt the Gravity Based Structures (GBS), one of widely used ocean structures, to implement the concept of large scale ONPP with Advanced Power Reactor 1400 (APR1400) model [1] which is the latest model developed by KOREA. Actually, the GBS type ONPP system has never been researched. In this paper, we present a new concept of nuclear power plant based on ocean environment to overcome the safety limitation of conventional land-based NPP and social problems, called NIMBY (Not In My Back Yard) or BANANA (Build Absolutely Nothing Anywhere Near Anybody). We also present the safety features of our concept and future works.