Off season is just as important as the regular triathlon season. It's a good time to do some activities you've been wanting to do but just haven't had time to do... i.e. mountain bike, snow shoe, hike, trail run, water polo, etc. It's important to change it up during off season so you keep your motivation when you need it most during the regular season. Also, it allows you to work on some imbalances you might have been dealing with the previous season.
What are your favorite off season activities?