Totally Not GG
Scout by Land: The marshes seem to creep up around you as you venture deeper into the swamp, spindly trees loom out of the oppressive fog. The going is slow, and Quicksand puts you in constant danger (DC 15 to avoid), but the heart of the swamp seems to be just ahead. If trapped in quicksand, a Wyrmling black dragon comes to investigate the thrashing (DC 18 to identify its age category), burps a gout of acid on the trapped scout, and then flees. Otherwise, a DC 20 Perception check spots the Wyrmling stalking the PC like a cat, at which point it promptly flees.
Scout by Air: The bogs this deep into the swamp seem to be covered in a light mist, limiting your visibility of the ground. From the sky, you can see many pools of standing water and thick mud amidst the few paths of solid ground, but your view is quickly obstructed by the flowing fog banks. (DC 20 Perception) While hovering over a particularly suspect area, you spot a small, black winged dragon about the size of a large dog that spots you as well. After a moment of surprise, it dives out of the sky and into the water of the swamp below.
The swamp is thick and oppressive, and progress is slow going. As you venture deeper into the swamp, you struggle to stay on solid ground, having long since abandoned the luxury of terrain that is both solid and dry. At points, the water deepens to the depth of a flowing river, at most others, though, it reaches at least up to your ankles. To compound your problems, the water is scummy and impossible to see in and a light, but pervasive mist limits your visibility beyond fifty feet or so.
After hours trekking through the swamp looking for dry ground to rest on, you notice a strange anomaly in the water about you… while the rest of the swamp has been composed of murky, scummy water full of frogs and snakes and birds, this area has much cleaner water in it, but no wildlife. It could be in part due to the flow you feel around your ankles – you suspect you are near another river – but you suspect that it may be something more sinister due to the suddenly apparent lack of wildlife. (Perception DC 20)
Draw out a largely featureless map, noting that the majority of the area is under a thin layer of water. Note an area of fast-moving water to the side of where the PCs are approaching from, and several mangrove trees around them. The black dragons have removed most of the cover from this area in favor of a complicated series of underground waterways that allow them to swim from one side of the solid ground to another. Next, secretly denote several random squares, particularly around the river to be centers of 20ft radius pools of quicksand.