The Arch

The Arch is one of the most dramatic natural underwater features in the Channel Islands — a spectacular rock formation off Santa Cruz Island that frames a sweeping blue-water view and serves as the centerpiece of one of Southern California's most beloved dive sites. Santa Cruz Island is the largest of the Channel Islands National Park islands and boasts some of the most pristine marine environments on the California coast, protected within the Channel Islands National Marine Sanctuary. The Arch site is accessible by live-aboard or charter dive boat from Santa Barbara, Ventura, or Oxnard, a crossing of roughly 20 to 25 miles that places divers in waters of extraordinary clarity and productivity. The arch itself is a natural erosional feature in the island's volcanic rock — a tunnel-like formation through which divers can swim while sunlight streams through the blue water beyond, creating a perfect natural frame for one of the Pacific Coast's most photographed underwater images. The surrounding reef is rich with the characteristic marine life of the Channel Islands' cold, nutrient-dense waters: kelp forests of giant bull kelp rise from the rocky substrate in dense, cathedral-like formations, providing habitat for a cascade of species through the water column. California sheephead, garibaldi, kelp bass, and calico bass work through the kelp and rocky reef. Harbor seals and California sea lions are regular companions at Santa Cruz Island sites, their underwater agility in comic contrast to their ungainly appearance on the surface rocks. Giant black sea bass — the recovering apex predator of California's reef ecosystem — have been increasing in sightings in the Channel Islands, and the Arch area is among the sites where encounters are most frequently reported. The cool water temperatures (typically 50 to 60 degrees Fahrenheit) require a drysuit or 7mm wetsuit, and the crossing from the mainland requires preparation, but the Channel Islands reward the effort with diving that ranks among the finest in the Pacific.