CalWave Power Technologies UG (CalWave) is developing the CalWEC, a submerged pressure-differential Wave Energy Converter (WEC) leveraging a fully submerged wave absorption mechanism which leads to higher survivability in extreme weather conditions. Extensive testing at 1:50 scale was completed in 2016, and limited testing at 1:20 scale was completed in late 2016. The results of both experiments validate CalWave’s numerical calculations and economic modelling, but more extensive testing was required to increase confidence in critical design measurements and system identification. CalWave sought support from the MaRINET2 program to continue medium scaled (1:20 – 1:30) tank testing. Two elements of the testing supported by the MaRINET2 program were particularly beneficial. First, testing at a relatively large scale reduced scaling errors due to viscous effects. CalWave preferred testing at 1:20 scale, though a smaller scale, such as 1:30 was used for certain tests assessing the device behaviour in extreme seas. Second, a testing campaign of several weeks amortized setup costs over more experimental hours, thus allowing full system characterization in-situ for reduced uncertainty and a richer data set for further design iteration.