The must do activity in Kakadu is a Yellow Waters Fishing Safari. The guide, Dean Jackson, is a brilliant naturalist and local historian as well as being a very patient, friendly, unpatronizing fishing guide. Three novice fisher-people did a half day tour starting at 6 am to catch the sunrise over the wetlands. It's worth staying at Gagudju Lodge in Cooinda so you don't have to drive miles to get there. Dean will fillet a fish for you and the chef at Gagudju can cook it that night for $20 per head. It is an extraordinary meal as most Barramundi eaten is farmed not wild. The best thing is how close you can get to the wildlife unlike the 40-50 people in the large boats that take the more famous Yellow Waters Cruises. Dean's knowledge of  the wetlands makes him an excellent guide if photography or twitching is your thing. Fishing is not compulsory. Terrific value for money for an activity that will make your holiday.