PURPOSE: To make a shelf serviceable to growth and breeding of underwater vegetable and to enable gathering of underwater vegetable and to enable gathering of fishery products by a method wherein a shelf is hung down in water to form an artificial sea bottom, and a pontoon is floated in a position near the artificial sea bottom.

CONSTITUTION: A shelf 1 is suspended in water for support in a state to be coupled to the lower end parts of cables 4, e.g. a wire, a chain, hung down from buoys 3 floating on a sea surface. Diffusing pipes 5 are mounted to the shelf 1, where occasion demands, to deaerate sea water and an underwater projector 6 is installed to project light in water. Or by pumping up sea water in deep having abundant dissolved oxygen onto the shelf 1 with the aid of a pump, a condition useful to growing and breeding of underwater vegetable and fishery products is created, and the shelf is functioned as a artificial seat bottom. A half-diving type pontoon 2 a part of which is protruded from a sea surface and which can be utilized for various facilities is floated in a position near the artificial sea bottom, and is moored to an anchor 8, seated on a sea bottom B, through a cable body 9.