Is the sea blue because it reflects the color of the sky?

Answer No, it is not. The color of the sea is based on the way it scatters and reflects light. The reds are generally absorbed, and the other colors, the greens and blues, are scattered with some reflection. Remember you're looking into the sea to see its color. Greens and blues are common because of what is in there and the way the light scatters and is reflected off of it.