There is a tidal variation of up to 4 metres, a very substantial change, especially since the harbour, being silted up with almost 10 million years of sedimentation, is rather shallow itself.

New Zealand's most tragic shipwreck occurred on the bar in 1863 when HMS Orpheus ran aground in clear weather with a loss of 189 lives.

As they crossed Te Tō Waka (the portage at Ōtāhuhu between the Manukau Harbour and the Tāmaki River), the crew believed they heard voices of people on the other side.

It had several portages to the Pacific Ocean and to the Waikato River, and various villages and pā (hill forts) clustered around it.

[6] In Te Kawerau ā Maki tradition, the taniwha Paikea guards the Manukau Harbour and Waitākere Ranges coastline.

[8] The surrounding bush clad hills had vast amounts of kauri removed for milling and shipped from a wharf on Paratutai to either the other end of the harbour at Onehunga for use in house building in the new city of Auckland, or along the coast to other New Zealand settlements.

One of the few separate earlier European settlements was Onehunga, from where some raiding of enemy settlements occurred during the New Zealand wars, and which later became a landing point for kauri and other products landed by ship and canoe from the south, the shipping route being shorter than the one along the east coast to the Waitematā Harbour.

[14] The harbour is popular for fishing, though entry to the water is difficult with few all-tide boat ramps; often local beaches are used.

Despite all that is precious about the Manukau, it is under ongoing threat from constant development and growth, with the pollution and damage that brings.

Currently, according to the State of Auckland Marine Report Card, the harbour has a D-rating overall, based on water quality, contaminants and sediment, and ecology.