Complex system design is increasingly adopting on risk and reliability analysis. Approach population and urban development expand in landscape island countries or countries with long coastlines, city planners and engineers resort to land reclamation to ease the pressure on existing heavily-used land and underground spaces using risk based design. Risk based design has also been used on system that use fill materials from seabed, hills, deep underground excavations, and even construction debris, engineers are able to create relatively vast and valuable land from the sea. An aquaculture industry is the fastest growing food producing sector in the world. Considerable interest exists in developing open ocean aquaculture in response to a shortage of suitable, sheltered inshore locations and possible husbandry advantages of oceanic sites. Adopting the concept of very large floating structure in aquaculture farming in ocean is like to produce more aquaculture product like seaweed. All being property and support for growing aquaculture industry. On risk analysis study of offshore aquaculture ocean plantation system is very important to determine the system functionality and capability that meet sustainable and reliability requirement. The research will qualitatively assess system risk and quantify mooring failure probability, maximum force and required number of mooring as well as associated cost.