We studied how optical characteristics of plain water chestnut (Trapa natans L.) are connected to morphological and biochemical characteristics. The measurements were performed on floating leaves of the selected type macrophytes. Reflectance and transmittance were measured in the range 280 nm to 880 nm. Morphological analysis of leaves include leaf thickness and specific leaf area. Biochemical analyzes included measuring levels of colorants (chlorophyll a and b, carotenoids, anthocyanins and UV absorbing substances). We have found that, in the UV territory reflectivity is low and there is no transmittance; in the visible range of the spectrum the peak of reflectance and transmittance is maximum in the green specter. In the NIR range of the reflectance and transmittance is high, but reflectivity is higher. The results showed that morphological parameters do not affect the reflective and refractive spectra. The biggest influence on the reflectance and transmittance, have UV-A and UV-B absorbing compounds; in light transmittance in the green spectrum also affects chlorophyll b.