Among various devices of wave energy converters (WEC), oscillating water column (OWC) devices are one of the concepts successfully deployed around the world. Hence, the necessity to design and develop the recent concept of dual-chamber OWC device attached to an existing coastal breakwater emerged. Former investigation in a wave flume already characterized the hydrodynamic performance of the device for a 1:25 scale model with frontal wave excitations. From this study, the effect of the incident wave direction is highlighted and the effect of the air compressibility on the device performances can be determined. The enclosed dataset refers to the experimental work developed at LNEC within the project Harbour OWC (PTDC/EME-REN/30866/2017) and considers the 3D effect of the incoming waves with a 14º angle of incidence. Data of free surface elevation along the tank and inside the device along with total pressure are presented.