As part of an investigation into the feasibility of an offshore combined wind/wave energy converting platform, comprising one or more wind turbines mounted on a floating structure in which a number of oscillating water columns (OWCs) are embedded, testing was carried out on a 1:50 scale model of the wave energy converting component of the platform. The model comprises two legs joined at one end at an angle of 90 degrees. A form of soft latching is implemented through the use of high and low-pressure plenums to which the OWC chambers communicate via air admittance valves. The model was tested in a number of configurations, subject to varying amounts of simulated power take-off damping and over a range of incident regular-wave periods. Platform motions, OWC chamber and plenum pressure and water column motions were recorded for each test. This paper discusses some considerations in the design, construction, instrumentation and testing of the model. Thermodynamic theory describing the flow of air throughout the system, based on the conservation of mass, is developed and related to the motion of the water columns. Representative results from the model testing in the time domain are presented. Finally, some conclusions are drawn from these results.