Manukau Harbour is the second largest natural harbour in New Zealand. Tidal flow is rapid, and the bar across to the Tasman Sea is extremely dangerous - NZ's most tragic shipwreck occurred in 1863 on this bar when the HMS Orpheus ran aground in clear weather with a loss of 193 lives.

Fishing is excellent with many popular species able to be caught year-round. Entry to the water is difficult with few all-tide boat ramps, often local beaches are used. Cornwallis, beside the Puponga Peninsular was the first site for the future city of Auckland. However because of fraudulent land sales and rugged conditions, the settlement was abandoned in the 1840s. The surrounding bush clad hills had vast amounts of Kauri removed for milling and was shipped from a Wharf on Paratutai to either the other end of the Manukau Harbour at Onehunga for use in house building in the new city of Auckland, or along the coast to other New Zealand settlements. The last mills were abandonded in the early 1920s.