In addition to reflection and refraction, there is also attenuation that occurs. Light is attenuated as it travels through media and different colors attenuate with different rates. Shallow water is clear with almost no attenuation, deeper water attenuates all red light and looks blue-green, and even deeper water also attenuates all the green light and looks blue. (Source: http://web.stanford.edu/class/cs148/pdf/class_13_reflection_and_transmission.pdf)
In addition to reflection and refraction, there is also attenuation that occurs. Light is attenuated as it travels through media and different colors attenuate with different rates. Shallow water is clear with almost no attenuation, deeper water attenuates all red light and looks blue-green, and even deeper water also attenuates all the green light and looks blue. (Source: http://web.stanford.edu/class/cs148/pdf/class_13_reflection_and_transmission.pdf)