You're in the swamp. The ground is wet. The air is wet. And the vegetation is bloated with water, which makes it a poor building material. As a result, one of the most challenging things to do is erect a dry shelter.
Find a dry spot. Of course, "dry" is relative, but a slight hill should be less wet than areas of lower elevation. It's also a good idea to learn how to spot and avoid run-offs. These sparsely vegetated, eroded spots are prone to flash floods, so they're not ideal for a shelter, especially when rainfall is likely.
Look for a space that's at least a little longer than your body and twice as wide, ideally with four trees at the corners. If you can't find a place with well-spaced trees, try driving sturdy wooden stakes into the ground. (Bamboo works nicely.) A rare benefit of building a shelter in a swamp is that it's relatively easy to plunge stakes into the soggy ground.
Measure and cut branches to build a frame. You'll need two rails that are longer than your body and long enough to connect to your trees or poles. Use a square lashing to secure each rail to the trees or posts. If you don't have rope, gather vines, which you can usually find in most swamp and jungle areas.
Once the frame is in place, cut shorter branches to lay across the frame as a platform, and tie them to the rails. When you're done, your swamp shelter should be strong enough to hold your full weight, and keep you off the ground and at least somewhat drier.
For padding and insulation, top off the platform with large leaves or cut sections of moss. And there you've got it: a fairly comfortable bed that's high above the moisture, not to mention beyond the reach of many animals and insects.