A floating marine structure which includes a first float disposed at the center and a plurality of second floats disposed around the first float, where the first float has a floating body made of a floatable material in a polygonal prism shape, a damping unit coupled to the bottom of the floating body at the center, having the same cross-section as the floating body, having a cross-sectional area larger than the cross-sectional area of the floating body, and reducing a shake of the first float in the sea, and at least one coupling hole formed at each side of the floating body. The second float has the same shape as the floating body and has coupling protrusions formed at sides facing the sides of the floating body and inserted in the coupling holes, and wherein the coupling holes are formed at alternate sides of the floating body.