Fish farm operators worldwide are planning to move offshore due to lack of available nearshore production sites in heavily utilized coastal zones, where there is increasing community opposition to coastal development and conflict with other usages such as shipping, fishing, tourism, conservation and recreation. Moreover, offshore sites provide more sea space and generally better water quality, which are needed to increase the production of healthy fish. This review paper begins with the definition of offshore for fish farming based on unified viewpoint and proceeds to highlight the challenges faced by going offshore. Next, the paper presents a review of designs of fish cages from conventional nearshore fish farms to next-generation offshore fish farms, which have to contend with a high energy environment. The fish cages may be divided into the open net cage system and the closed containment tank system. The open net cage system can be categorized further into 5 types. The advantages and disadvantages of the various fish cage designs will be discussed. Further, different types of cage designs are compared with the view to guide feasibility of offshore fish farming. Co-location with other synergetic industries is discussed as a possible example of future offshore fish farms.