A robotic ocean farm includes a plant support means such as a grid, with a submersible towing system incorporating means for navigation of the support grid in the open ocean, and means for positioning of the support grid in a first surfaced position for sunlight exposure of the plants and a second submerged position for nutrient gathering by the plants. The submersible towing system incorporates one or more tow boats connected to a forward periphery of the grid, each of the tow boats incorporating a propulsion system for navigation of the grid and maintaining lateral tension in the forward periphery of the grid. Additionally, one or more reaction boats are connected to an aft periphery of the grid. Each of the reaction boats incorporates a propulsion system for maintaining lateral tension in the aft periphery of the grid and reacting in concert with the tow boats to maintain longitudinal tension in the grid. A system for harvesting multiple independently operating farms incorporates a harvesting station which is placed or positions itself to meet the farms at predetermined locations during their voyage to harvest and replenish the plants carried on the farm grid. Base stations, separately or as a part of the harvesting station, communicate with the farms provide mutual support and informational exchange for optimized operation of the farms.