For those who don't mind getting sweaty, who love long bumpy 4wd tracks, for those who can deal with walking where there are no tracks, and who like to carry some equipment Koolpin in Kakadu is a must.
You will need to get a permit, so book early.
You need to pick up a key from Mary River Roadhouse. $50 deposit.
From here take the Gunlom Road to the T-Intersection and turn right.
On the Map it is now refered to by it's local name Jarrangbarnmi.
There is a basic campground with a single drop toilet.
Campfires were still allowed in 2009.
Opposite the campground is a sacred and prohibited area so please consider the wishes of the traditional owners.
The lower levels of the river are also close to croc country so I wouldn't personally swim there, although I have seen many doing just that. Like we in the know say On top of rocks no crocs, in other words get up high enough that crocs cant swim before you do.
The walk is just to follow the river, a few hints.
From the campsite walk back up the road about 600m to a track on the left this is a shorter way to the safe swimming areas.
At thye first waterfall go up the left hand side and cross over the river at the top, you may have to get your feet wet. Here is the start of the fantastic swimming areas, sometimes called the giants staircase there are multiple large swimming holes. You can walk up the gorge as far as you want provided you make it back to the camp that night (you can stay at Mary River Roadhouse or Gunlom campground and make this a day trip). If your lucky you might see some rock art, although it is not publicised. Usually you will only see one or two other groups of people which make this the best water feature in Kakadu. A great walk, fantastic gorge, awesome rock features, cool large beautiful swimming and no-one else. This is the best place in Kakadu in my books, go before august before the water starts to drop, you can still go in November and swim and is still beautiful, the waterfall may not be flowing like you'd expect. Why deal with the hundreds at Jim Jim when with a little more effort you could go here. In fact it so good I shouldn't be telling you about it.