One of my favourite places near Alice Springs is Redbank Gorge, about 220km west of Alice Springs in the West MacDonnell Ranges. The road is sealed except for the entry into the gorge carpark, which is about 8km of rutted dirt track. It can be accessed by normal car most of the time, but you’d have to take it very easy. A 4WD is a better option.
Once at the carpark, there is a strenuous 1.2km walk along the creek bed to get to the gorge. If you like clambering over rocks and wading through deep sand, then you’ll enjoy the walk. Otherwise, just keep plugging away at it, as the gorge at the end is well worth the effort. Because the gorge is so narrow, it gets little sunlight, so the water tends to be chilly. This is OK as you have to work hard to swim through the gorge and this keeps you warm. Also, some flotation is a good idea. I’d recommend something like a small car inner tube, or a floatie ring, as anything big like an air mattress won’t fit through.
At several points through the gorge, you have to climb over rocks worn smooth by millenia of water flowing over them. This can be tricky, and I would suggest always having someone with you in the gorge. It’s not a tourist spot, so if you get injured, you may have quite a wait for someone to come along and find you. Most visitors to Redbank Gorge stop at the entrance and take photos there before leaving. I’d say only about a third of them attempt the swim through, and maybe 5% make it all the way through. There used to be a chain in the rock about 3/4 of the way through, but it was washed away in 2010, and I don;t know if it’s been replaced. You can still get through (I have done it since the chain vanished) but it’s difficult and most tourists give up at this point.
If taking a camera, make sure it’s waterproof, or in a waterproof case.
Finally, keep an eye out for snakes in the water. I’ve seen one in the six times I’ve been to the gorge, and due to the cold it was very sluggish and easily avoided. Just make sure you see it first!