This dataset provides the in-situ measurements from a Pressure-sensing Inverted Echo Sounder (PIES) 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 campaign also deployed three CTD moorings, a slocum glider, and another bottom pressure recorder. The PIES measurements include bottom pressure and the round-trip travel time from the IES, which can be used to derive equivalent steric height through regression.