Interesting one here. Keys in two steps to Echinochloa telmatophila (Ligule: none; Lemma awn length: up to 35mm (the longest I measured) with a number of them between 25 and 35). E. telmatophila is known from Auckland only according to Flora V. Also, the description on the Flora has the racemes 0.5 - 3 cm - this has racemes up to 5cm - and leaf-blade width 7mm - this plant has leaf-blades twice that. Growing in slow-moving ditch water with Persicaria, Nasturtium, Cyperus etc. @reinderw There are more plants in this ditch if you want to investigate yourself.