These data present suspended particle size distributions collected by the U.S. Geological Survey (USGS) Pacific Coastal and Marine Science Center within two embayments of San Francisco Bay. Data were collected at one site in San Pablo Bay and one site in Grizzly Bay from June through August 2019, by deploying a Sequoia Scientific Laser In-situ Scattering and Transmissometry instrument (LISST 100x) from a small vessel near pre-established USGS instrument moorings. At both sites, data were collected on six dates at three depths, generally near the water surface, at mid depth, and near the sediment bed, for 1-3 minutes at each depth. LISST volume concentrations are most accurate when the optical percent transmission is above 30, as light passing through the sample volume is unlikely to be scattered by more than one particle. One file (ERO19PBP04) was removed due to poor data quality throughout the file. These files contain all samples collected; judgment should be applied when using them. Users are advised to check metadata and instrument information carefully for applicable time periods of specific data.