The Nature of Sea Water 39 
THE COLOR OF SEA WATER 
Sea water exhibits a deep blue color in deep regions, a 
lighter greenish blue in shallow regions of the ocean. The 
blue color is supposed to be caused by tiny particles scatter- ° 
ing the light of the sun, and since they are very small they 
scatter the blue light more than the other visible colors. In 
shallow regions the bottom itself reflects up some light and 
this plus the blue gives a greenish hue. At other times the 
ocean is colored a deep brown or even a vermilion red by col- 
loidally suspended mud or by the presence of dinoflagellates 
as in the Red Sea and the Gulf of California. Dinoflagellates 
are simple little one-celled creatures possessing intricate cel- 
lulose cases, and two little hairs (called flagella) by which 
they move. 
On a dark night aboard ship you may note that the bow 
spray of your ship shines brightly. The phenomenon is gen- 
erally spoken of as “phosphorescence of the sea” though it 
really has nothing to do with the tiny amount of phosphorus 
present in sea water. It is better to call it “bioluminescence” 
inasmuch as it is light produced by myriads of tiny sea organ- 
isms. The glow is due mainly to the presence of the tiny 
dinoflagellates (Ceratium and Noctiluca, et al.). Since they 
are particularly abundant in warm water, sea luminescence is 
found most often in the tropics. 
FISH WITH “FLASHLIGHTS” 
Some animals produce a luminescent slime which they 
secrete over their bodies giving them a brilliant glowing ap- 
pearance. One variety of squid is capable of squirting out a 
bright fiery cloud. He lives in the dark nether regions of the 
ocean where the inky cloud that most squids eject would be 
