In the second episode of the first season of the television series Top of the Lake, a beautiful Maori legend is mentioned:
You know there's a,
Maori legend about this lake
That says there's a demon's heart at the bottom of it.
It beats, it makes the lake rise and fall every five minutes.
Does it rise and fall?
Yeah. Yeah, it does.
It was this, um, a warrior
That rescued a maiden from a giant demon called tipua.
And he set fire to the demon's body while it slept
And burnt everything but his heart.
And the fat melting from the body formed a trough.
And the snow from the mountains ran down to fill it to form this lake.
The setting of the series, Laketop town and the lake mentioned in the quote, is fictional. However, apparently at least some of the scenes were filmed at Moke Lake, near Queenstown.
I'm wondering if the story is based on actual Maori tales, or if it was invented by the show's writers. The Wikipedia article on tipua, the only name mentioned in the story, is not helpful.