In the mid 20th century, drilling for hot water at Húsavíkurhöfði revealed water that turned out to be hot seawater, too rich in minerals to be suitable for heating houses but perfect for bathing in. Geosea uses that water. While soaking in Geosea you'll enjoy panoramic view over the Skjálfandi bay and the mountains around it. I loved visiting Geosea, it's the only hot spring/spa in Iceland where you can bathe in warm sea water.