I hate to throw water on any of the parks, but they can't ALL be the largest. Let's see if we can sort it out and make some sense about the claims. Keep in mind that the info cited in this article is a moving target. This is a rapidly evolving industry, and indoor water parks are constantly opening and expanding. To the best of my knowledge, this article contains info that is currently accurate.
On the pages that follow, we'll explore places such as the Water Park of America (America's biggest!), Fallsview (North America's largest!), and The World Waterpark (North America's largest!). See? We've already uncovered multiple claims to the same title. Let's dive in and get to the bottom of this, shall we?