Lake Tenkiller is a 12,900-acre U.S. Army Corps of Engineers reservoir on the Illinois River in Cherokee and Sequoyah counties in eastern Oklahoma — widely considered the clearest and most scenic lake in Oklahoma and the premier scuba diving and water clarity destination in the state. Tenkiller Dam impounds the Illinois River in the Arkansas River watershed, creating a deep clear reservoir in the Cookson Hills of the Cherokee Nation that draws boaters seeking water quality and scenery unavailable at the larger, murkier Oklahoma reservoirs to the west. The lake’s exceptional clarity — visibility regularly exceeding 15 feet — and its limestone bluff shoreline in the Cookson Hills make Lake Tenkiller the most visually distinctive reservoir in the Oklahoma directory. Largemouth and smallmouth bass, crappie, catfish, and walleye provide a quality fishery across Tenkiller’s deep clear basin and the Illinois River arm. The communities of Gore, Vian, and Cookson on the lake’s shoreline anchor the primary marina and service infrastructure. Find Boat Services lists verified boat repair, motor service, electronics installation, trailer repair, and winterization providers serving Lake Tenkiller within 25 miles across Cherokee and Sequoyah counties.