Abstract: A submersible positive buoyancy habitat structure for use in rearing shell fish and the like in an open ocean environment. The habitat structure is designed to take advantage of the mass movement of water due to wave action in a vertical plane to provide continuous flushing of the habitat. To this end, the habitat structure is based on a generally tubular body having impervious side walls open at both ends with one end tethered to the ocean bottom. The open ends of the habitat are covered by a grill to keep predatos out and a screen to keep adolescent shell fish within the structure. A venturi device is provided at the lower end of the structure to enhance downward vertical flow of water therethrough. Variable buoyancy flotation devices are described and an arrangement providing a plurality of habitat structures sharing a common flotation device is disclosed. A feeding device for use with the habitat structure is provided.