The apparent total color of sea by comparison with samples tested by "MAERZ & PAUL: A Dictionary of Colors, 1950". We find green colors of Forel Scale: Forel n. 5 in waters with Pheophyceae, Sargassum, and Rhodophyceae; Forel n. 6 waters in stones with the Cirripedia, the barnacle Tetraclita squamosa; the alpine green in waters with Trichodesmium exuthraeum. Emerald green in the localities with blooms of the diatom Coscinodiscus. The central portion of the bay, 150 Km[squared] hole-green, full of larvae of shrimps Penaeus schmidti; some shoals of shrimps moves its pleopods and by displacement of botton with diatoms and reddish sediment produces a rust color spot in surface of waters seen by fishermen. The estuaries are Isabell color, and caramel. That is a preliminar survey, to future comparison, because to day Sepetiba Bay is not polluted. But futurelly, it will be polluted by an harbour for 3.000,000 tons of iron ore, and by a quay for cargo boats, and siderurgy mills, airports, and other industries. Several polluted waters of Guanabara Bay are black and asphalt color, and cub color. That colors are not found in Sepetiba Bay to day. In 1965, we do not find the "red waters" and "red tides" with blooms of dinoflagellates in Sepetiba Bay, that they are present sometimes in Guanabara Bay with mortalities of fishes. Sepetiba Bay is not biologic problem, to day, is not polluted. The fig. 3 shows a map of transparence of waters by the disc of Secchi and a relation is given of color and transparence, in Sepetiba: Forel color 5: transparence 2.8 m to 2.9 m; Forel n. 6: 2.0 m; Forel color n. 7: 1.0 m to 1.5 m. Moss green waters: 0.6 to 1.5 m; hellebore green waters: 0.9 to 1.5 m; emerald green waters: 2.0 m to 2.2 m; In Guanabara Bay, into the polluted Enseada de Inhaúma: asphalt color waters: 0.02 - 0.05 m; and in black waters: trasnparence of 1 cm. The extintion koeficient of light is indicated in explanation of the fig. 3.