The Wairau Lagoons are located 7.5km south-east of Blenheim at the mouth of the Wairau river. Both ecologically and archeologically they are of national significance. Along the boulder bank which separates the lagoon from Cloudy Bay are a series of Maori archaeological sites including middens, campsites and burial grounds. Archaeological evidence suggests that these represent some of the earliest humans to arrive in New Zealand.
It is believed that the moa hunters herded moa from the Wairau plain and surrounding hills along this bank from which there was no possible escape. A number of extinct water birds are also present including the flightless goose and giant coot. Many of the moa skeletons held in museums around the world come from the boulder bank.
At the time of European settlement the Wairau lagoons stretched some distance inland and contained a large body of fresh water wetlands to the west of the present lagoons. This has since been drained and is now used for farming. However, the treated water from the Blenheim oxidation ponds is discharged through a series of man made wetlands which somewhat compensates for this. The remaining saline lagoons attract around 70 species of birds, a number of which breed there. Several new migrants have also been sighted for the first time in New Zealand there. A number of fish species are also common in the warm shallow water, partly the reason for the bird life. Galaxids, bullies, and herrings are common as well as larger fish such as kahawai and baracouta which feed on shrimps and the common mud crab Helica crassa.
Vegetation is typical of South Island salt marshes with a mix of low salt resistant plants, including glasswort Salicornia australis and numerous creeping species. On higher ground stunted plants of saltmarsh ribbonwood and coprosma are present.
A feature of the lagoons is a shipwreck, the Waverly. This vessel was towed here after its useful working life. It was used for flood control, and for target practice by the army.
A walking track from Harding's road provides access to the lagoons.