Peak amplitude values recorded at source and receive hydrophones during a two-vessel marine sparker seismic survey conducted by the U.S. Geological Survey (USGS) in April of 2021 off the coast of Santa Cruz, California (USGS field activity 2021-619-FA) are presented. On the source vessel (R/V Parke Snavely; RVPS), near-field data were recorded using a broadband spherical reference Reson TC4034 hydrophone positioned 1-meter below the sparker source (either a SIG ELP790 or an Applied Acoustics Delta sparker) along seven depth site transects ranging between 25 and 600 meters. On the nearly stationary receive vessel (R/V San Lorenzo; RVSL), omnidirectional Cetacean Research CR3 hydrophones were positioned between 10- and 20-meters water depth below the vessel to record the far-field signal. Data are presented in csv format, accompanied by combined scatter plots per depth site and mean-filtered curve plots for visualization purposes.