When it comes to pools, the motto in St. Louis is: "If we build it, they will come." Over the past decade, municipalities have been trying to outdo each other in the water-park department, which means there are plenty of good public water parks to choose from. Using a scientific formula that considered nonresident admission fees, types of water attractions, comments from young patrons and lifeguard surliness, we have come up with this year's winner: the just-opened North Pointe Family Aquatic Center in Ballwin. It may not have as many waterslides as some of the other well-established (and pricier) pools, but a couple of eleven-year-old boys reluctantly pried their eyes off a skinny, bikini-wearing sixteen-year-old of the opposite gender long enough to describe the waterslide, which renders the swimmer blind during the descent, as "wicked." The kiddie pool boasts a few very fast slides for the toddler set, as well as a giant bucket that periodically dumps gallons of water on them. And for the swim-diaper crew, water fountains squirt out of the ground like a sprinkler. North Pointe also has a retro feature attraction: a competitive pool, equipped with lap-swimming lanes and diving boards. But even the old has been improved -- the pool's got a tree swing. The center is open daily, Memorial Day to Labor Day, from 11:30 a.m. until 7 p.m.; residents pay $3 or $4, depending on age, while nonresidents pay $6 or $7. Season passes are available.