A floating multi-unit structure to be used for various operations offshore, on lakes, rivers, etc. It comprises two types of main units, termed propulsion/support unit and operative unit, respectively. Each such main unit includes at least one functional member. The two main units are adapted to be interconnected through their functional members and functionally integrated in a manner resulting in synergetic effects of the totality of the interconnected units. The propulsion/support unit includes one or more vessels equipped with propulsion machinery and equipment to meet support functions. When the propulsion/support main unit is comprised of several vessels, the individual vessels are functionally integrated in a manner resulting in a synergetic effect providing the propulsion/support main unit with the intended combined properties. The operative main unit includes one or more barge members equipped to perform the intended operations. When the operative main unit comprises several barges, the individual barge members are functionally integrated in a manner resulting in a synergetic effect providing the operative main unit with the intended combined properties.