Lake McKenzie, also known as Boorangoora, in the K'gari Wolrd Heritage Area on Fraser Island, with its clear water and white sand, is the most iconic place on the Island. It images, along with dingos, is what comes to people's mind when they think of K'gari. Here is a guide on how to get there and what to do when you are there.

Lake Mckenzie on Fraser Island/K'gari
The names K'gari and Fraser Island
The island and surrounding area were home to the Butchulla people, and in recent years, the use of indigenous names has increased on the island. At the time of writing this and based on official sites I have read, the Butchulla name K'gari, which is pronounced gurri and means paradise, refers to the World Heritage Area. Fraser Island island is still the name of the island, but as the world heritage area and the island are basically the same place, you can switch the names around if you want.
About the lake
Lake McKenzie, also known as Boorangoora in the Butchulla language, is a perched lake. Basically, Fraser Island is made up almost entirely of sand, and this sand acts as an aquifer storing and filtering large amounts of rainwater. The lake sits in a hollow in the aquifer so that the water table is exposed.

The pure blue water of Lake Mckenzie on Fraser Island/K'gari
Fish do live in the lake, but due to the purity of the water, lack of nutrients and mild acidity, they are very few. So chances of seeing any are very slim. There is of course no fishing permitted in the lake.
Getting there
There are 3 ways to get around the island, and that is to join a tour, walk or drive a 4 wheel drive. Most tours seem to be arranged from Rainbow Beach of Hervey Bay, but there are some day tours from the Kingfisher Bay Resort. Most tours of the island will include Lake McKenzie.
Walking is an option, and Lake McKenzie is a stop on the K'gari Great Walk. There are also 2 walking tracks from Kingfisher Bay to the lake. One is 10 kms and the other is 13 kms. So that is at least a 20 km return walk, though you can hike into Lake McKenzie and camp if you want.
Driving is easy if you have a 4 wheel drive. The road runs from the east coast through Central Station to the lake and then on to Kingfisher Bay or River Heads on the west coast. So it is easy to get to from either side of the island.

4 wheel driving to Lake McKenzie
Being dingo safe
Dingos are an issue at the lake. They are attracted to the food scraps people might leave lying around, so eating on the lake shore is forbidden. Instead, there are a couple of picnic areas set back from the lake next to the car park inside dingo-resistant fences. Dingoes being relatively shy are likely to turn up early in the morning before people arrive, and late in the afternoon or evening after most people have left. Though they can of course turn up at any time.

Warning sign about dingoes at Lake McKenzie
Activities
Swimming is the main activity at the lake. There is a gently sloping shelf of shallow water leading to deeper water. Most people just hang out in the shallower water. Because of the wide shallow area, it is actually great for throwing a ball around or other activities like that.

Swimming at Lake McKenzie on Fraser Island/K'gari
Some people bring kayaks or stand-up paddleboards. The lake is 1.2 kms long and nearly 1 km wide, so it is a great place for paddling around. There are multiple beaches around the lake that they plan to open up in the future. But for now, you can paddle across to your choice private beach.

Stand up paddle boarding at Lake McKenzie on Fraser Island/K'gari
It is also good to relax on the white sandy beach. There is some shade from the small trees on the edge of the beach, but you should consider bringing your own shade if you plan to be on the beach for any extended period of time. Though you have to leave the beach to eat or drink anything but water.

Worth bringing your own shade to Lake McKenzie if you plan to relax on the beach there
Being environmentally friendly
So if you are thinking of getting in the water, they recommend that to protect the lake you don't wear any sunscreen, perfumes, oils and so on. Being a perched lake, the water flows in but not out, so whatever oily things you have on your skin will go into the lake and just stay there. If you are worried about sunburn, then wear a big floppy hat and a rash vest to protect your skin.
Overall
There are lots of lakes on Fraser Island/K'gari, with Lake McKenzie being the most popular and the most beautiful. You know how people's cameras automatically adjust the colours to make the images look better or people use Photoshop to do the same thing - nope, not here, those photos are exactly how the lake looks. Definitely worth several hours of your time while on the Island.

Lake McKenzie looks exactly like the photos