Open-sea aquaculture systems and methods are provided, which employ a semisubmersible platform with vertical columns, having storage and maintenance facilities for supporting aquaculture. Systems comprise a rigid assembly of aquaculture cages, with vertical cavities having forms configured to receive the corresponding vertical columns of the semisubmersible platform. The rigid assembly is mechanically connected to the semisubmersible platform in operational positions: (i) a raised position in which the rigid assembly encloses the corresponding vertical columns in the vertical cavities to limit a horizontal movement of the rigid assembly, and (ii) a lowered position in which the rigid assembly is below the corresponding vertical columns. Systems further comprise a control unit configured to control the mechanical position control mechanism to lower the rigid assembly upon occurrence of specified rough sea conditions, or whenever needed, and to raise the rigid assembly upon specified conditions.
