Fig. 2. A 3-dimensional structure of the daily illumination (µW m^-2 nm^-1) in the visible light spectrum (400-700 nm) measured at 5 m depth in Gulf of Eilat, Red Sea, in front of the Interuniversity Institute for Marine Science. Measurements were conducted on a cloudless day on February 14, 2001. The spectrum was scanned between 5:00 h and 18:30 h, with readings taken every 30 min at 2 nm intervals.