PURPOSE: To enhance leisure quality on the sea by forming a box, having floating stability, such as a hollow conical trapezoid and a cylinder, of raw material like FRP, and fixing a weight to anchor it on the bed of the sea or moving it with a power machine.

CONSTITUTION: A box having good floating stability such as a hollow conical trapezoid, a cylinder, a truncated pyramid and a prism is formed out of FRP or a similar raw material. Moreover, it is designed to hang a weight to anchor it on the bed of the sea of to move with a power machine. For higher leisure quality, a sunshade is fixed or a stand is installed on the upper part.