The hydrodynamic forces acting on an oscillating multi-degree-of-freedom wave energy converter reaction body are characterized using scaled experiments and CFD simulations. Curves indicating how the hydrodynamic coefficients vary with Keulegan-Carpenter number (KC) and Reynolds number (Re) at four different scales, ranging from 1:75 to 1:36, are presented for multiple degrees of freedom. Understanding scale dependence is identified as important, as although representative KC numbers can be generated, the dissimilitude between the laboratory and full-scale Reynolds numbers requires careful consideration when inferring full-scale coefficients from the experiments. To address and examine this, CFD is used to replicate a number of these model-scale tests and provide simulations at full-scale. These results provide an important validation of some scaling trends but also reveal interesting discrepancies at low KC. We will show how these hydrodynamic relationships are replicated in different modes of motion, and illustrate their importance when building numerical models of WECs.