The existing pressures on coastal areas are prompting the off-shore transfer of economic activities such as aquaculture, transportation, tourism, energy, leading to new challenges for the sustainable use of the sea and calling for integration of different activities in the same area. This paper conceptually designs a multi-use off-shore area in a mild sea, whose purpose is the setup of an energetically self-sustained fish farm. The climate conditions for aquaculture and renewable energy production are assessed first. The features and production of the fish farm are then designed, as well as the renewable energy system offering the power support. A new dedicated tool is presented and adopted for the set-up and sizing of the electrical system required for the power stabilisation and energy supply in case the multi-use area is not grid-connected. The layout and payback time of the multi-use are finally examined, showing that wave energy systems are still far to make such installation economically competitive.