Nature Bank

Water sky is a phenomenon that is closely related to ice blink. It forms in regions with large areas of ice and low lying clouds and so is limited mostly to the extreme northern and southern sections of earth, in Antarctica and in the Arctic. The dark clouds over open water have long been used by polar explorers and scientists to navigate in sea ice. For example, Arctic explorer Fridtjof Nansen and his assistant Hjalmar Johansen.  Source