O'Neill Bay and the cliffs around Raetahinga Point are the remnants of a Miocene era volcanic crater complex.

[3] The 100 metre thick sequence is composed of at least 11 thin andesite flows, interspersed with breccia, scoria and lapilli tuffs.

The bay's name, Te Awakauwahaia, or Kauwahia for short, refers to the ancestress Erangi.

[4] After falling in love with a man at Puketōtara to the north of Te Henga, Erangi decided to evade the guarded walking paths to the hill, by swimming to O'Neill Bay, and eventually to Te Waharoa Point, with her child on her back.

Eventually her father was suspicious of her actions, and discovered her lover by piercing the sand underneath her cloak with his spear.