A number of individual barrier units form a floating barrier wall each comprising a housing formed in the general shape of a highway barrier having a top wall, a bottom wall, opposed end walls, and, opposed side walls interconnected to form a hollow interior which is preferably partially or completely filled with a foam material. A ballast weight is secured to each barrier unit, either inside or outside of the hollow interior, to maintain them in an upright position in the water. Cables, couplers and/or other connectors are employed to mount adjacent barrier units end-to-end to form a barrier wall which can encircle a vessel or otherwise isolate an area within a seaport or other body of water to provide security.