fortifications, paths, walls.. hammer and hoe are what you use to conquer the swamp.. don't expect to walk in and steal the riches of the swamp.. you gotta pacify it a little first.. really just a few walls here and there makes life much easier, and paths are a necessity.. but then you drain the iron out no problems..

stuff like this

https://steamcommunity.com/sharedfiles/filedetails/?id=2783183435

https://steamcommunity.com/sharedfiles/filedetails/?id=2783183493