[1][2] The reserve covers the area from Mean High Water Mark out to half a nautical mile into the sea, along three kilometres of the coastline.

[1][4] The main geological features of the reserve are exposed greywacke, large grey-green rocks formed during the Jurassic Period studded with marine fossils.

[1] Both the Tāwharanui Peninsula and offshore sea area were sources of food and other resources for Māori hapū until well into the 20th century.

There is archaeological evidence on the peninsula of shell middens, snapper and other fish bones, and 18 species of shellfish.

Care must also be taken when anchoring to avoid damaging the sea [1] The reserve is one of four places in New Zealand where people can snorkel to see abundant crayfish.