Lake McKenzie is a sublime place to swim. And on the day we were there, we were the only group (14 people!). The lake is a "perched lake", meaning it is located above the water table. It is fed ONLY by rain water, and the only way water can exit is through evaporation. A layer of bonded mud, sand and vegetation (peat) called "humate" acts like a huge swimming pool liner, keeping the water inside.
Because the water is pure, swimmers are asked not to wear sunscreen or oils or use soap and shampoos when swimming. Car camping has been banned by the lake, which has cut down on the amount of litter and water contamination which previously occurred there.
The water temp was approximately 23 degrees - perfect!
Fraser Island has about 40 perched lakes.
Here are my photos of swimming in the lake previously - on 24 Jan 2001