According to the 1925 New Zealand Official Yearbook, it drains about 1,800 cu ft (51 m3)/sec[6] via the 20 km (12 mi)-long Wairaurāhiri River into Foveaux Strait 10 kilometres to the west of Te Waewae Bay.

[7] Traditionally, Ngā Puna Wai Karikari o Rakaihautu say the lake was dug by rangatira Rākaihautū on his journey south with his ko.

[9] Geologists say it's a glacial lake,[10] formed near the Hauroko Fault (it and other faults in the area have slipped several kilometres)[11] in early carboniferous granites and metamorphic rocks, on the higher ground, with much more recent Hauroko Formation Eocene - Oligocene sediments such as calcareous sandstone, on the lower ground, towards the southeast.

The island is famous for the discovery of a burial site of a Māori woman in 1967, who is known as "the lady of the lake" by Southland locals.

Believed to have been placed on the burial site sometime between the late 16th century and 17th century, possibly around 1660, the woman was laid to rest wearing a flax cloak and a dog skin collar with weka feather edging around her neck, and was seated upright on a bier made of sticks and leaves.

This led to the belief that this woman was of high-ranking status, and it was later discovered through an archaeological investigation that she was a chieftain of the Ngāti Moimoi tribe.

[22] The lake is one of the few not yet colonised by invasive water weeds, except the bulbous rush, Juncus bulbosus,[23] so it retains plants such as Nitella stuartii algae, Callitriche petriei water-starwort, Isoetes kirkii quillwort, Pilularia novaezelandiae pillwort fern, Trithuria inconspicua waterlilies[10] and Charales fibrosa.