The current development pace of wave energy converters indicates the possibility of the deployment of these converters as arrays at commercial scale. The accurate predictions of wave loads, motion characteristics, and power requirements are critically important for the design of these devices which are in sufficiently close proximity to experience significant hydrodynamic interactions. The oscillation of each body radiates waves assuming that other bodies are not present. Some of these radiated waves that can be considered as incident waves interact with the bodies of the array causing diffraction phenomena while others radiate to infinity. The fluid response between arrays can affect overall power generation and could increase or decrease power generation compared to an isolated device. The power generation due to hydrodynamic interaction depends on separation distance, geometrical layout, direction of the incident wave, geometry in the array, incident wave length, mooring configurations, control strategies, etc.