The story Maaka tells about the taniwha in Wellington Harbour is a true part of Maori mythology, though told somewhat differently from tradition: Whataitai and Ngake were sea taniwha who created Wellington Harbour, which was once a lake in which these taniwha lived. But Ngake was restless and smashed his way through to nearby Cook Strait. Whataitai tried to get out a different way and became stranded on dry ground. It is said that his spirit took the form of a bird named Te Keo, which flew to the top of Wellington's Mt Victoria and mourned (tangi), hence the name of the mountain, Tangi te keo. (via the Te Ara online encyclopedia)
One of the newspaper headlines seen in the opening credits is "Police Close Gates of Hell Near Bucket Fountain". This is a reference to events from the pilot episode, Demon Girl (2018).
Newspaper headlines in the opening credits: "Vampire Ate My Kitten, Hutt Woman Claims"; "Karori Toddler Attacked by Ghost Poodle"; "Hairy Man Seen Near Seatoun Salon"; and "Police Close Gates of Hell Near Bucket Fountain"
As available on The CW network, this episode has been retitled, "The Not Ness Monster," probably because this reference is more familiar to western mythology than the original title, which is a reference to Maori myths.