A concrete module having a buoyant center core with a light weight concrete outer shell. The modules have lengthwise and width wise passages on non-common planes. The modules are connected with rods, cables or other interconnecting methods through the passages. The sides of the modules may be curved to allow the modules to fit securely together along the vertical corners in a straight line without bowing or bending. The top of the module may be constructed with reinforcing ribs for strength. The size of the modules are designed to be transported using standard hauling trucks and moved with skid loaders or fork lifts. The modules have common sizes and connecting passages between modules to make uniform modules to allow custom designed docks and other floating structures to be configured. A variety of brackets are provided for attaching other structures to the modules making up the floating structure.