DESCRIZIONE
Semi-submersible fish-farming system, such as a fish pen (1), which can be located in at least two different semi-submerged positions, a first position (15) and a second position (16), by ballasting and de-ballasting, the system comprises a floating collar (2) comprising a ring-shaped or polygonal lower buoyancy member (7), a ring-shaped or polygonal upper buoyancy member (9), a plurality of pillars (8) connecting the buoyancy members (7, 9), a net cage (3) suspended from the floating collar (2) and a net roof (5) closing off the top of the net cage (3), wherein -the net cage (3) is suspended from the lower buoyancy member (7) or the pillars (8); - in the first position (15), the system is floating on the lower buoyancy member (7) and the pillars (8) and upper buoyancy member (9) is above the water surface; - in the second position (16), the lower buoyancy member (7) and the major parts or all the extension of the pillars (8) is below the water surface.