Wetlands: Swamps, Marshes, Bogs, and Fens (2016)

From the introduction:

Not many natural terrains are more diverse than wetlands. Wetlands contain a multiplicity of vegetation and wildlife. These ecosystems team with insects, amphibians, turtles, and birds of all types. The variety of the flora is astonishing. Mosses, lichens, trees, bushes, shrubs, peat, ferns, reeds, and grasses, just to name a few, can all be found in wetlands. When constructing your campaigns, introducing wetlands can create unique experiences and challenges for characters. When traveling on their quest, an adventuring party will invariably come across wetlands. Or least, they would if they were traveling in the real world. Use wetlands to diversify the types of terrains in your campaigns. A well-described and presented wetland can create a memory that will last a lifetime.

Of course, not all wetlands are the same.