Crooked Lake is 108 acres in size with an maximum depth of of 70 ft./21.3 m. It is one of the Tully Lakes, a group of six lakes (along with Tully, Tracy, Mud,Green, and Song) called kettles because they were formed when large chunks of glacial ice melted and left a depression. The Tully Lakes are at the southern end of the Tully Valley and the northern end of the Tioughnioga Valley. The two valleys are divided by the St. Lawrence Seaway Divide, which causes Tracy and Mud to drain to the north into Lake Ontario and Song, Green, and Tully to drain to the south into the Susquehanna River. Crooked Lake is unique because it is the only lake of the six that drains in both directions as the divide runs right under the lake. This means that the lake is also in both valleys.
Quite often kettles are perfectly round. Tracy Lake is a good example of this. Other times, kettles can be extremely irregular in shape. Crooked Lake is a good example of this as it winds in and out with many coves and several small islands.