A composite material containing inclusions of spherical shells in which each spherical shell encapsulates a rubber core with ferrite loading. The inclusions are embedded in a matrix material of syntactic foam. The spherical shells are made from glass and therefore acoustically transparent and in combination with the cores are statically stiffer than the surrounding matrix material. The composite material with the matrix material and inclusions allows the composite material to be acoustically dissipating with a stiffness in which the energy of forces associated with undersea platforms is resisted.