It’s time for the Chippewa Valley’s resident water nymphs – The Ski Sprites – to finish their season of water skiing. Part of the festivities will include the area’s only sand castle contest. Starting at noon (register at 11:30am), before and alongside the last show of the Ski Sprites Water Ski Show Team’s season, this 2nd annual event will see teams compete to build the best granular fortress they can imagine. The big ski show takes place at 2pm. Singer Matt Wahl will perform all afternoon. (Lake Altoona Beach, Eau Claire; Monday at noon; $10 to build a castle, free to watch, $3 to park)