Indoor water parks are a relatively recent phenomenon. Nobody had the brilliant idea of moving water slides, sprayers, and other fun ways to get wet into a weatherproof and temperature-controlled environment until the early 1990s when a Wisconsin Dells hotel added a modest water play structure to its indoor pool. Soon after, Todd Nelson opened his first indoor water park resort in the Dells and then parlayed it into a mega-resort, the African-themed Kalahari. Nelson and his family recently opened their fourth Kalahari, the biggest one yet, in Texas. Read about the first family of indoor water park resorts in my Funworld feature.