Anacapa Island in the context of "Scuba equipment"

Scuba diving is an underwater diving mode where divers use breathing equipment completely independent of a surface breathing gas supply, and therefore has a limited but variable endurance. The word scuba is an acronym for "Self-Contained Underwater Breathing Apparatus" and was coined by Christian J. Lambertsen in a patent submitted in 1952. Scuba divers carry their source of breathing gas, affording them greater independence and movement than surface-supplied divers, and more time underwater than freedivers. Although compressed air is commonly used, other gas blends are also employed.

Open-circuit scuba systems discharge the breathing gas into the environment as it is exhaled and consist of one or more diving cylinders containing breathing gas at high pressure which is supplied to the diver at ambient pressure through a diving regulator. They may include additional cylinders for range extension, decompression gas or emergency breathing gas. Closed-circuit or semi-closed circuit rebreather scuba systems allow recycling of exhaled gases. The volume of gas used is reduced compared to that of open-circuit, making longer dives feasible. Rebreathers extend the time spent underwater compared to open-circuit for the same metabolic gas consumption. They produce fewer bubbles and less noise than open-circuit scuba, which makes them attractive to covert military divers to avoid detection, scientific divers to avoid disturbing marine animals, and media diver to avoid bubble interference.

The Santa Barbara Channel is a portion of the Southern California Bight and separates the mainland of California from the northern Channel Islands. It is generally south of the city of Santa Barbara, and west of the Oxnard Plain in Ventura County.

It trends east–west, is approximately 130 kilometres (70 nmi) long and averages about 45 kilometres (24 nmi) across, becoming narrowest at its easternmost extremity where Anacapa Island is about 30 kilometres (16 nmi) from the mainland. During the last ice age, the four northern Channel Islands, including Santa Rosa Island, were conjoined into Santa Rosae, a single island that was only five miles (8 km) off the coast.

The Anacapa Island State Marine Reserve (SMR) is a protected marine reserve located off the coast of Southern California, encompassing the area of water immediately north of Anacapa Island. Established to safeguard the marine ecosystems and biodiversity of the region, the reserve is one of the thirteen Marine Protected Areas (MPAs) of the larger Channel Islands National Park network.

Anacapa State Marine Reserve covers an area of 11.55 square miles (29.9 km) and has a shoreline span of 3.1 miles (5.0 km).The reserve protects sandy beaches, extensive rocky shores, surf grass beds, kelp forests, deep offshore sand, and rocky seafloor to depths greater than 700 feet (210 m) below sea level.The reserve includes a Special Closure area of approximately 1 square mile (2.6 km) to protect seabirds and marine species.

Santa Rosae (also spelled Santarosae) was, before the end of the last ice age, an ancient landmass off the coast of present-day southern California, near Santa Barbara County and Ventura County, of which the northern Channel Islands of California are remnants. At its largest, Santa Rosae was roughly 3-4 times bigger than the northern Channel Islands of today, nearly 125 kilometers (78 mi) from east to west. Between about 20,000 and 5,000 years ago, Santa Rosae lost about 70% of its land mass to post-glacial rising sea level, leaving behind a vast submerged landscape currently being explored by scientists. San Miguel, Santa Rosa, Santa Cruz, and Anacapa Island comprise the unsubmerged portions of Santa Rosae today. This island was about 5 miles (8.0 km) offshore. It broke up between about 11,000 and 9,000 years ago, and the present northern Channel Islands took their shape after the continental ice sheets melted and sea levels rose by about 100 meters.

There is evidence to suggest that a now-submerged island, Calafia, lay between Santa Rosae and the mainland.

The Chumash are a Native American people of the central and southern coastal regions of California, in portions of what is now Kern, San Luis Obispo, Santa Barbara, Ventura, and Los Angeles counties, extending from Morro Bay in the north to Malibu in the south to Mount Pinos in the east. Their territory includes three of the Channel Islands: Santa Cruz, Santa Rosa, and San Miguel; the smaller island of Anacapa was likely inhabited seasonally due to the lack of a consistent water source.

Modern place names with Chumash origins include Malibu, Nipomo, Lompoc, Ojai, Pismo Beach, Point Mugu, Port Hueneme, Piru, Lake Castaic, Saticoy, Simi Valley, and Somis. Archaeological research shows that the Chumash people have deep roots in the Santa Barbara Channel area and have lived along the southern California coast for millennia.