Barrenjoey Head is situated at the northernmost peninsula of the Northern Beaches at the junction of the Hawkesbury River and the ocean.

The aquatic reserve covers approximately 30 hectares including the rocky shore around Barrenjoey Head, extending from the northern end of Palm Beach around Barrenjoey Head to the northern end of Station Beach, and out to 100m offshore.

The reserve is focused on conserving marine biodiversity of the rocky shore fringing Barrenjoey Headland. The rocky shore has a diversity of habitats and associated marine life, including four of the five types of habitats described for NSW rocky shores (platform, crevice, rock-pool and boulder habitats).