The sky appears blue sometimes because it is reflecting the vast ocean expanse on the Earth's surface

The blue color of the sky is caused by Rayleigh scattering - sunlight is scattered by gas molecules in the atmosphere, with shorter blue wavelengths scattering more than longer red wavelengths. The ocean appears blue because it reflects the sky's blue light, not the other way around. This is a common misconception about the cause of the sky's color.