According to local Maori legend, the Moeraki Boulders are the remains of eel baskets, kumaras, and calabashes that washed onto the shore after the wreck of Arai-te-uru, a large sailing canoe. The rocky shoals that extend out from Shag Point represent the petrified hull of the canoe, the Maori say, and the nearby rocky promontory represents the body of the captain.

The Moeraki Boulders are actually a type of huge stone that is recognizable for being highly spherical. They can be found scattered around the Koekohe Beach near Moeraki, a small town on New Zealand's Otago coast. This section of beach has been protected by the government as a scientific reserve. The Moeraki Boulders are not the only rocks of this size and shape; there are huge spherical boulders molded over millions of years on other New Zealand coasts as well.

Weighing several tons each, the Moeraki Boulders originally formed about 60 million years ago during the early Paleocene. Some can measure up to nine feet across. For millions of years, the boulders lay buried underground, covered up over time. Slowly, they have emerged as waves wash away the mudstone.