Tidelands are the territory between the tide line of sea coasts and lands lying under the sea beyond the low-water limit of the tide, considered within the territorial waters of a nation.
In the United States, the upper limit of tidelands is determined by the mean high tide as established by a chart datum, defined as a 19-year period based on the lunar cycle known as the National Tidal Datum Epoch.
The Dos Cuadras Offshore Oil Field is a large oil and gas field underneath the Santa Barbara Channel about eight miles southeast of Santa Barbara, California. Discovered in 1968, and with a cumulative production of over 260 million barrels of oil, it is the 24th-largest oil field within California and the adjacent waters. As it is in the Pacific Ocean outside of the 3-mile tidelands limit, it is a federally leased field, regulated by the U.S. Department of the Interior rather than the California Department of Conservation. It is entirely produced from four drilling and production platforms in the channel, which as of 2009 were operated by Dos Cuadras Offshore Resources (DCOR), LLC, a private firm based in Ventura. A blowout near one of these platforms – Unocal's Platform A – was responsible for the 1969 Santa Barbara oil spill that was formative for the modern environmental movement, and spurred the passage of the National Environmental Policy Act.