This dataset provides the conductivity, temperature and depth (CTD) measurements from the CTD sensors on a WireWalker profiler on a full-depth mooring deployed by the SWOT prelaunch field campaign. The campaign was designed to test the performance of several instruments/platforms in meeting the SWOT Calibration/Validation (CalVal) requirement. It was conducted near the SWOT CalVal crossover location, about 300 kilometers west of Monterey, California between September, 2019 and January, 2020. The WW samples the upper 500 m of the water column, while the deep ocean below 500 m are measured by fixed-depth CTDs https://doi.org/10.5067/SWTPR-CTD01. The campaign also deployed another two CTD moorings, a slocum glider, one bottom pressure recorder and one Pressure Inverted Echo Sounder.