Have you seen freshwater bubbling up at the coast?

“Most people don’t realise there are areas of the seabed where the freshwater leaks through,” said Dr Mountjoy.

“These underwater springs could discharge substantial volumes of freshwater, but we don’t know enough about large coastal aquifers around New Zealand. We realised that fishermen and divers might have come across them and not even give a second thought to how important they might be."

Freshwater springs can be identified by different colour or temperature close to the seabed, or a shimmering pattern because of freshwater and saltwater mixing.They can appear as a pockmark in the seabed or as distinctive patterns and can be marked by temperature changes.

The public appeal follows efforts in 2023 to map the Waiwhetu Aquifer beneath the Hutt Valley and Wellington Harbour. The team recorded video footage and acoustic soundings of freshwater flowing out of several hundred pockmarks in the harbour, the largest of which are more than 100m wide.

Dr Mountjoy says these underwater springs are an important component of understanding on land aquifers. “They could be points of salinisation of the aquifer if too much water is used on land. Potentially they could be used to find undiscovered water resources. We are seeing more drought-prone and water-scarce areas, so the science is needed more than ever. Knowing more about offshore freshwater springs gives us so much more information about our freshwater and how these areas might be further studied for the benefit of society.”