There is a great interest in the availability of acoustic coatings for maritime systems applications, in particular for the reduction of radiated noise in water. The purpose of this paper is to give an overview of recent results regarding the design of such materials, which are classically of two main types: the micro-inclusion technology and the Alberich-type coating. In both cases, resonances of inclusions are exploited. Here, the concepts are extended to configurations with several layers of periodic arrangements of soft and rigid inclusions. The analysis is done using the finite-element technique. The results show a wide variety of acoustical phenomena, allowing us to customise the design according to different applications.