By late August, deep temperatures have climbed to 57-58. Daytime darkness is around 90 feet depth. September is a great time to dive the lake. Expect afternoon thunderstorms almost every day after mid-August. Cisco Beach, on the east side, has 3 dive areas with anchored dive buoys.
Water skiing is the main draw here.
Three state parks provide boat access to the lake. At one time, there was a miniature dive store at the beach. Logan is your closest source of air fills. When you're too sore to water ski any more, drive around to Cisco Beach on the east shore. This popular site has anchored dive buoys and shaded diver prep areas.