Ocean water temperatures were collected from May 14, 1992 to August 22, 2023 (these logger deployments are ongoing) from 10 meters benthic depth, at Van Damme State Park, Mendocino County, Northern California. Water temperatures were collected with Onset Hobotemp® and TidbiT® temperature loggers in degrees Celsius. Data are presented as daily averages of 10-minute minimum intervals. Ocean water temperatures were collected to document long-term temperature conditions on the bottom at the level of the reef. Loggers were placed 1 meter off the bottom on stainless steel cages used to monitor juvenile abalone and sea urchin recruitment at this reference location. Water temperatures are presented as daily averages for the period of record. Some data gaps exist due to equipment failure, loss, or rough conditions precluding placement of data loggers. The data gaps are listed in the “Problems/Issues” section below. These data are unique in that they are benthic seawater temperature data (1 meter from the bottom where the benthic animals live) which can be used to compare with the more readily available sea surface temperature data.