Well, jungles are different depending on country. But there are a lot of reasons to be in swimming shorts and sandals: it is too hot and humid, you venture into the jungle thicket only a few times a day, but spend most time around your camp preparing wood for fire, fixing accomodation, or go for sightseening and fishing on a canoe (there is a lot fo shaded area in jungles where you can see a lot of animals, also more fish is in shaded areas, therefore you do not burn under the sun). You sweat a lot and therefore stay as much naked as you can. Even some light work during the day can cause overheating.
Aquapac seems to be a good idea - not too shiny to stand out too much.