A floating unit capable of attaching to another floating unit by locks for constructing a floating structure, said floating unit comprising: a floating body being in the form of a hollow polygonal shape as viewed from above, wherein the floating body comprises an upper surface, a lower surface, and a plurality of lateral surfaces connected to said upper and lower surfaces, said floating unit being characterized in that: said upper surface and said lower surfaces of the floating body comprise at least one upper engaging surface and at least one lower engaging surface respectively on each associated side of said polygonal floating body, wherein the upper and lower engaging surfaces ( 200, 202) are respectively adapted in order to be fitted with a locking surface of said lock, thereby, attaching said floating body to a floating body of another floating unit, and said upper and lower engaging surfaces ( 200, 202) of said floating body respectively comprise notches, each of which has a contact surface inclined outwardly and downwardly of said floating body, wherein the width of said notches located toward the inside of said floating body, wherein the width of said notches located toward the inside of said floating body is more than that located towards the outside in the form of widening indentation, wherein, in use, the corresponding contact surfaces of the notches of said upper engaging surface and the corresponding contact surfaces of the notches of said lower engaging surface are snugly in contact with the locking surfaces of said locks, thereby, attaching said floating unit to another floating unit without using fastening means, wherein the floating unit further comprising an external device installing channel, wherein the channel is in the form of a semicircular channel extended from the upper surface to the lower surface, such that the channel will facilitate connection of the external connecting device in both horizontal and vertical directions. a floating body being in the form of a hollow polygonal shape as viewed from above, wherein the floating body comprises an upper surface, a lower surface, and a plurality of lateral surfaces connected to said upper and lower surfaces, said floating unit being characterized in that: said upper surface and said lower surfaces of the floating body comprise at least one upper engaging surface and at least one lower engaging surface respectively on each associated side of said polygonal floating body, wherein the upper and lower engaging surfaces ( 200, 202) are respectively adapted in order to be fitted with a locking surface of said lock, thereby, attaching said floating body to a floating body of another floating unit, and said upper and lower engaging surfaces ( 200, 202) of said floating body respectively comprise notches, each of which has a contact surface inclined outwardly and downwardly of said floating body, wherein the width of said notches located toward the inside of said floating body, wherein the width of said notches located toward the inside of said floating body is more than that located towards the outside in the form of widening indentation, wherein, in use, the corresponding contact surfaces of the notches of said upper engaging surface and the corresponding contact surfaces of the notches of said lower engaging surface are snugly in contact with the locking surfaces of said locks, thereby, attaching said floating unit to another floating unit without using fastening means, wherein the floating unit further comprising an external device installing channel, wherein the channel is in the form of a semicircular channel extended from the upper surface to the lower surface, such that the channel will facilitate connection of the external connecting device in both horizontal and vertical directions. said upper surface and said lower surfaces of the floating body comprise at least one upper engaging surface and at least one lower engaging surface respectively on each associated side of said polygonal floating body, wherein the upper and lower engaging surfaces ( 200, 202) are respectively adapted in order to be fitted with a locking surface of said lock, thereby, attaching said floating body to a floating body of another floating unit, and said upper and lower engaging surfaces ( 200, 202) of said floating body respectively comprise notches, each of which has a contact surface inclined outwardly and downwardly of said floating body, wherein the width of said notches located toward the inside of said floating body, wherein the width of said notches located toward the inside of said floating body is more than that located towards the outside in the form of widening indentation, wherein, in use, the corresponding contact surfaces of the notches of said upper engaging surface and the corresponding contact surfaces of the notches of said lower engaging surface are snugly in contact with the locking surfaces of said locks, thereby, attaching said floating unit to another floating unit without using fastening means, wherein the floating unit further comprising an external device installing channel, wherein the channel is in the form of a semicircular channel extended from the upper surface to the lower surface, such that the channel will facilitate connection of the external connecting device in both horizontal and vertical directions.