The steep cliffs of the Kosado Hills stretch all the way down to the seafloor. Therefore, it is possible to pump up deep seawater from a depth of 200 meters even in areas close to the coast. Deep seawater is nutrient-rich with high levels of phosphorus and magnesium. This is because the water is pumped from an area where which no light reaches – thus, photosynthesis does not take place and minerals in the water are not depleted. This deep seawater of Sado Island is influenced by the “Sea of Japan proper water” Sado Island deep seawater is very clean, with a water temperature of around 1°C throughout the year – it is contained in a very cold, freezer-like environment.

Sado deep seawater is used not only as drinking water, but also for cultivation of Amaebi (Alaskan Pink Shrimp) and Benizuwaigani (snow crabs). The water is used for cooling to maintain freshness of products during transport. The water contains well-balanced minerals, and due to its high quality, is served as yawaragi water (water to drink with sake) at famous izakayas (Japanese-style pubs) in the Tokyo metropolitan area.