A floating production plant for farming of marine organisms, such as fish, is described, comprising: a number of closed tanks (60) filled with water to contain the organisms, and also associated pumps and pipelines, where each tank comprises water inlets (52,59) and water outlets (4b, 51) for circulating water that is collected from the surrounding sea, and said water outlets (4b, 51) are placed, in the main, in a centrally located and internally open middle section (24), where the middle section extends from the bottom of the tank (60) and vertically up to, at least, above the water level in the tank.