Strait's Blue Ice

The photo was taken from the shores of Mackinac Island, MI.
 
The ice only appears blue when it is sufficiently consolidated so that air bubbles do not interfere with the passage of light. The ice appears blue when the red (long wavelengths) part of white light is absorbed by ice, and the blue (short wavelengths) light is transmitted and scattered. The longer the path light travels in ice, the bluer it appears.