The reliability of the models elaborated for recreating the spectra of the light attenuation coefficient, d, , K λ on the basis of its measured values at 1-3 wavelengths was studied. The coefficients of the "one-point" (490 nm) model, elaborated earlier by A. Reinart and A. Herlevi, were tested and approved using 43 new spectra of underwater irradiance measured in 1999-2000. A new version (named C-model) allowing recreation of the spectrum of d, K λ on the basis on its measured values at three

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... avelengths was elaborated and tested by statistical analysis. The C-model was found to enable to reconstruct the spectra of d, K λ with high reliability. Both models gave truthful values of d,PAR K (mean value of d, K λ in the region 400-700 nm). For the estimation of the reliability of the experimental initial data, the values of d, K λ derived from in situ measurements by an underwater spectrometer LI-1800 UW and an instrument ac-9 were compared. The results showed that d, (ac-9) K λ is mostly lower than d, (LI-1800 UW), K λ the differences increasing with wavelength.