A floating marine structure having floats, comprising: a first float disposed at a center; and a plurality of second floats disposed around the first float; wherein the first float has: a floating body made of a floatable material in a polygonal prism shape; a damping unit coupled to a bottom of the floating body at a center, having the same cross-section shape as the floating body, having a cross-sectional area larger than a cross-sectional area of the floating body, wherein the damping body reduces movement of the first float in the sea; and at least one coupling hole formed at alternate sides of the floating body, and wherein each 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 each coupling hole has an inlet hole formed inwardly perpendicular to the side of the floating body and a locking hole extending at a right angle from an end of the inlet hole, the coupling protrusion has a first locking portion protruding outward from the side of the second float and a second locking portion extending at a right angle from an end of the first locking portion, and the second locking portion is inserted in the inlet hole and then slid into the locking hole, thereby coupling the first float and the second float to each other, and wherein first through-holes are formed from a top of the floating body to the locking holes, second through-holes are formed in the second locking portions, and the first float and the second float are coupled to each other by inserting coupling pins into the first through-holes and the second through-holes with the second locking portions fitted in the locking holes. a first float disposed at a center; and a plurality of second floats disposed around the first float; wherein the first float has: a floating body made of a floatable material in a polygonal prism shape; a damping unit coupled to a bottom of the floating body at a center, having the same cross-section shape as the floating body, having a cross-sectional area larger than a cross-sectional area of the floating body, wherein the damping body reduces movement of the first float in the sea; and at least one coupling hole formed at alternate sides of the floating body, and wherein each 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 each coupling hole has an inlet hole formed inwardly perpendicular to the side of the floating body and a locking hole extending at a right angle from an end of the inlet hole, the coupling protrusion has a first locking portion protruding outward from the side of the second float and a second locking portion extending at a right angle from an end of the first locking portion, and the second locking portion is inserted in the inlet hole and then slid into the locking hole, thereby coupling the first float and the second float to each other, and wherein first through-holes are formed from a top of the floating body to the locking holes, second through-holes are formed in the second locking portions, and the first float and the second float are coupled to each other by inserting coupling pins into the first through-holes and the second through-holes with the second locking portions fitted in the locking holes.