This line shapefile contains bathymetric contours at 10-meter intervals for the offshore area of Half Moon Bay, California. In 2007, the California Ocean Protection Council initiated the California Seafloor Mapping Program (CSMP) to create a comprehensive seafloor map of high-resolution bathymetry, marine benthic habitats and geology within the 3-nautical-mile limit of California's State Waters. CSMP has divided coastal California into 110 map blocks, each to be published individually as United States Geological Survey Open-File Reports (OFRs) or Scientific Investigations Maps (SIMs) at a scale of 1:24,000. Maps display seafloor morphology and character, identify potential marine benthic habitats and illustrate both the seafloor geology and shallow (to about 100 m) subsurface geology. Data layers for bathymetry, bathymetric contours, acoustic backscatter, seafloor character, potential benthic habitat and offshore geology were created for each map block, as well as regional-scale data layers for sediment thickness, depth to transition, transgressive contours, isopachs, predicted distributions of benthic macro-invertebrates and visual observations of benthic habitat from video cruises over the entire state. These data are intended for science researchers, students, policy makers, and the general public. This information is not intended for navigational purposes.The data can be used with geographic information systems (GIS) software to display geologic and oceanographic information. The map that show these data are published in Open-File Report 2014–1214, "California State Waters Map Series--Offshore of Half Moon Bay, California." This layer is part of USGS Data Series 781. U.S. Geological Survey. (2013). Contours (10m): Offshore of Half Moon Bay, California, 2007. California State Waters Map Series Data Catalog: U.S. Geological Survey Data Series 781. Available at: http://purl.stanford.edu/qk466kv0273. MBES and side scan data for CC_Block01 to CC_Block11 are a combination of 400KHz Reson 7125 and 244 KHz Reson 8101 sonar data collected aboard the F/V Quicksilver by Fugro Pelagos, Inc. (FPI) and the R/V VenTresca by the Seafloor Mapping Lab (SFML). CC_Block00 (Stinson Beach) and the area surrounding the San Francisco Bay mouth were surveyed entirely by SFML using the Reson 8101 aboard the VenTresca. Prior to data collection, a series of planned survey lines were created using the survey navigation and planning softwareWinFrog (FPI) or Hypack Max GOLD from Hypack, Inc (SFML). An Applanix POS/MV system with TrueHeave processing was used to provide position and attitude data for each vessel during data collection and accounted for vessel motion such as heave, pitch, and roll (position accuracy ± 2m, pitch, roll and heading accuracy ±0.02°, heave accuracy ± 5% or 5cm). KGPS altitude data were used to account for tide cycle fluctuations and sound velocity profiles were collected with an Applied Microsystems SVPlus sound velocimeter. This layer is presented in the WGS84 coordinate system for web display purposes. Downloadable data are provided in native coordinate system or projection.