Maroi legend believes that the boulders are actually the remains of eel baskets. The scientific explanation is much more complicated, but rather than regurgitate Wikipedia here is a link to their explanation.
Besides seeing these interesting boulders, I tried a Southland (south end of the South Island) treat…a cheese roll. It’s simply a piece of bread with melted cheese and onion, rolled up, coated with butter then baked or grilled. So easy, yet so good.