If you intend to carry everything yourself, then a large, great fitting and good quality top-loader rucksack is essential. If you are on a supported jungle trip then often a holdall or kit bag is better, though you will still need a tough day sack with a breathable back-system. Keeping things dry is the priority. Use a large dry bag to line your back pack and then at least one lighter dry sack to keep all your night time clothing and sleeping kit in. For safety, a separate, small, waist pouch or equivalent should be carried at all times (SOP kit).