Under The Red Sea was Hass’s second English language book. It described his first expedition to the Red Sea in 1949. Packing his diving gear and cameras, het set off alone from Vienna- in true pioneering fashion- to Port Sudan to begin of one of the greatest diving adventures ever undertaken. He encounters giant manta rays, sharks and extensive coral reefs and becomes the first person to take photos of many of these creatures in their underwater habitat.
Hass returned to the Red Sea in 1950 with his diving team, and using cameras designed by Kurt Schaefer, shot the movie Under The Red Sea.