The study investigated how much groundwater flows into the sea in Osaka Bay, Japan. Researchers used different methods to measure this, like looking at the temperature near the seabed and using a seepage meter. They found that the farther from the coast, the less groundwater flows into the sea. The measurements from the temperature and seepage meter methods matched up, showing that the results were reliable. Overall, about 36.7% of the water flowing from rivers into the sea actually comes from groundwater.