If you've ever wanted to go to Arnhem Land for any amount of time but lacked decent reason to apply for a permit to enter (and you WILL need to apply for a permit), Garig Gunak Barlu National Park is probably one of the best options you can get.
You'll probably be starting your day in Darwin - the bitumen an dirt drive from there through Kakadu National Park to Jabiru, the largest town on the border outside Arnhem Land, will take the best part of a day anyway, and even when you arrive you may not be able to cross over into Arnhem Land straight away.
Why? Well, because you have to drive through a saltwater crocodile infested river first of course, and the tide may be too high when you arrive for even the best 4-wheel-drive to manage. You may also need to stock up on last-minute supplies: Garig Gunak Barlu National Park has no fuel, no drinking water, no food, no supplies.
Once you do get across it's red dirt road for the next 8 hours, and under the terms of your permit you are not allowed to stop and get out of your vehicle for any reason bar the most dire of emergencies . Once you get past the town of Oenpelli (which you may also apply for a permit to briefly visit) you likely won't see another living person, not even driving by. The road can be treacherous even in the dry season with parts disintegrating into fine sand, and you need to keep alert for Kangaroos, buffalo and packs of wild horses crossing the road at a moments notice. Also, take note of the only signposts and road markings you're going to see - these will likely be indicating that the stretch of road you are travelling on doubles as an airstrip for the Flying Doctors, so look out for landing aircraft.
Small rivers may look like tempting places to stop, but there is ALWAYS the very high risk crocodiles will be just under the surface of the muddy waters, and you are a very long way from help indeed.
Once you reach Garig Gunak Barlu National Park and have checked in with the ranger, find yourself a shady spot near plenty of dead wood - shade for the burning hot days, wood for the freezing cold nights, and to keep the (actually scarce) mosquito's off. Settle down, relax - you have plenty of time and few distractions.
You can walk and drive around and through the parks many waterside and forest trails, visit the large lake hidden in the woods to photograph the thousands of migrating birds (but beware the wild pigs), go fishing from one of the inlets, charter a boat across to the ruins and graveyards of the Victorian military settlement. A decent guide can walk and talk you through the fascinating history of this early colonial presence that met with great successes and greater failures. On the way back go fishing from the boat, and look out for giant sea turtles!
The only thing you cannot do is swim. In fact, you are not even supposed to get within 3 metres of the waterline. There are many, many crocodiles. People have been taken, people will be taken - and they are so fast at powering out of the water, you will likely never even see them come at you. (Date of experience: Aug, 2008 )