In July 2025, researchers from the University of Hawaiʻi at Mānoa and the Scripps Institution of Oceanography completed a two-week offshore electromagnetic imaging survey. The work was funded by the Hawaiʻi State Legislature and conducted via the Natural Energy Laboratory of Hawaiʻi Authority (NELHA).
What were they searching for?
Scientists aimed to detect a potentially massive reservoir of fresh or brackish water beneath the seafloor—extending far beyond the island’s traditional near-shore freshwater lens.
Why does it matter?
If confirmed, this offshore aquifer could explain long-standing discrepancies between measured coastal water discharge and expected groundwater recharge. It may also present an important new freshwater resource for the region.
Where did the idea come from?
Initial signs of a buried offshore aquifer were spotted in 2018, when researchers noticed unusual groundwater behaviors that didn’t match existing models. The suspected reservoir may be trapped beneath volcanic rock and ash layers and extend miles into the ocean.
How did they investigate it?
Using seafloor electromagnetic sensors and a towed array that sent low-power signals, researchers gathered geophysical data across the leeward coast of Hawaiʻi Island—from north of Kiholo Bay to south of Kailua-Kona.
What’s next?
Data analysis is now underway. If an offshore freshwater source is confirmed, it could reshape how island hydrology is understood and managed—and potentially bolster water security in the face of ongoing drought and population growth.
Read more: Big Island Now article
Researcher’s Site: Powered by the Natural Energy Laboratory of Hawaii Authority | Freshwater Beneath the Sea – 2025
