I remember reading somewhere recently about why the sea is sometimes turquoise as at Cala Mitjana in Menorca.One theory is that it is seaweed but I decided I should look into this phenomina. Search as I may I could not find any information on Cala Mijana's turquoise colour. I decided to extend my search and this was my first mistake. Do you know how muchthere is on sea colour from NASA downwards? If you really want to see just type "why is the sea blue" into anybrowswer. if you prefer to to stay with my precis then read on!I mentioned particles in seawater. Any particles suspended in the water will increase the scattering of light. Some types of particles particularly the cells of phytoplankton, or algae contain light absorbing substances.
The most important light absorbing substance in the oceans is chlorophyll. Chlorophyll has a green pigment which absorbs the red and blue portions of the light spectrum to carry out photosynthes the essential plant process for growth. The overall effectis that green light is reflected. Thus the the ocean and seas with high concentrations of phytoplankton will appear in varying shades of blue-green or sometimes turquoise.