Originally Posted by 2MuchMark

Actually, it is!

Water is molecule made of 3 atoms (2 Hydrogen, 1 Oxygen). This molecule has 3 modes of vibration including 2 stretching vibrations of oxygen-hydrogen bonds (which occur at v1 = 3650 cm−1 and v3 = 3755 cm−1. Absorption due to these vibrations occurs in the infrared spectrum of light, making the water slightly blue.

Most of the blue we see in water is reflected by the sky, but not always.

Science, Bitches!