What you are looking at here is the biggest,,,

….estuary in the South Island of New Zealand.

The Waimea Inlet is the largest enclosed estuary in the South Island. It is 3,455 ha in area, with an internal coastline of 65 km. Episodes of heavy sedimentation occurred in the 1960s and 70s affecting some of the more enclosed parts of the estuary.

And that is how the local council TDC (Tasman District Council) report it so.