Coasts

Very deep (up to 100s of metres), narrow, elongated basins which are largely subtidal.

Similar in some respects to Category E estuaries, these have shallow basins and narrow mouths, usually formed by a spit or sand barrier. However, Category F estuaries have complex shorelines and numerous arms leading off a main basin.

Shallow, circular to slightly elongated basins with simple shorelines and extensive intertidal area.

Shallow, circular or slightly elongated basins with simple shorelines and wide entrances that are open to the ocean.

These occur where the mouth of a main river channel connects to shallow lagoons.

Elongated basins of simple shape and several to ten metres depth.

Very shallow basins (several metres depth). They are often elongated and run parallel to the shore.

The seaweed known colloquially as nori in Japanese - used for making sushi - or karengo in Maori has been reclassified by an international team of scientists including NIWA's Dr Wendy Nelson.