Coldwater is a ribbon lake, occupying the trough of a glacial valley. The surrounding ridges rise dramatically to heights of more than above the water. The length of the lake is about while the maximum width is no more than half a mile (0.8 km). The water surface is above sea level and the surface area is . The total watershed of Coldwater Lake is about . Coldwater Creek drains or 33% of the total, South Fork Coldwater Creek drains or 38%, and another or 30% drains directly into the lake. Several smaller lakes or glacial tarns are part of the watershed; the named ones are Heart Lake and Snow Lake, which both flow into Coldwater Creek before entering Coldwater Lake. Mount Whittier, the highest point in the basin at , sits at the head of the Coldwater Creek valley.