The gaint ones that pull the baubatons carriage in The Goblet of Fire and the scalely ones that only Harry and Luna can see in Order of the Pheonix or The Half Blood prince - I cant remember which!
You do a triwizard tournament - a swim race (the 2nd challenge was in the lake), a fire building race (the first challenge involved fire breathing dragons) and geocaching or orientering race (the third involved finding their way around a maze)
