I just read a NYTimes article by Andrew Keh on the Finnish fun-time game of swamp soccer, played in a calf-deep mud-field…so it might better be named mud-soccer. Kew discusses activities in the town of Hyrynsalmi, so if you get there, prepare to have your shoes and socks sucked off your feet by the deep swamp-muck.
If you look up the article, be sure to scroll down to the end (ehem, bare butts).