no, the water molecules are responsible.White light, which comes from the sun, is actually made up of waves of different wave lengths representing all colors of the spectrum. Water molecules absorb a specific part of this light: the wavelengths corresponding to the colors red and yellow. Now when we subtract these components to the incident light, it remains essentially ... blue. That;s why water molecules return a depleted light red and yellow, rich blue. In areas where biological productivity is high, the chlorophyll contained in phytoplankton absorbs the blue component and the light shifts to green. In a cave there is no sky and the water is blue.(white light come from the sun)