You're swimming in Kahana Bay on the Windward side, and suddenly you hit a cold cloud of sea water. Your swim has probably led you to a submarine groundwater discharge site.
Ground water can pop through sediment patches on the sea floor or through freshwater springs.
Native Hawaiians once were known to fill gourds from these sources for drinking water. With related concerns about the balance of nutrients in reef ecosystems, University of Hawaii researchers are trying to document predictable patterns. They have finished their first year of research at Kahana Bay and are about to start the second. Then they plan to move the research site to the south part of Kaneohe Bay, to investigate seepage sites and identify locations affected by pollution past and present. Craig Glenn, geology and geophysics professor, Gary McMurtry, an associate professor of oceanography, and doctoral student Geoffrey Garrison plan to measure the rate and quantity of submarine groundwater discharge.