Manukau Harbour, often called the 'Big Muddy', is the second-largest natural harbour in New Zealand, located on Auckland's southwestern coast. This expansive, shallow estuary covers 394 square kilometres and is characterized by its significant tidal flows and silt-laden waters, the result of millions of years of sedimentation. The harbour mouth is a narrow, 1.8-kilometre-wide channel between the Waitākere Ranges and the Āwhitu Peninsula, opening into a broad, roughly square basin. While its muddy appearance is due to easily stirred light sediment rather than pollution, the harbour supports a rich ecosystem teeming with shellfish, crabs, and baitfish. It offers a diverse and often underrated fishery, providing excellent inshore angling opportunities within a short distance of New Zealand's largest city, particularly well-suited for smaller boats when coastal conditions are rough.