Bear Lake is a natural freshwater lake on the Idaho-Utah border, about 109 square miles in size and split nearly equally between the two states. The lake is called the "Caribbean of the Rockies" for its unique turquoise-blue color, which is due to the refraction of calcium carbonate deposits suspended in the water. Bear Lake is at least 250,000 years old and was formed by fault subsidence that continues today, slowly deepening the lake along the eastern side. [1]