Amusement parks are starting to put the "oh" in H2O. By upgrading their water park offerings, operators are starting to reap the benefits of drawing a wider audience while giving their guests reasons to slip and slide their way through longer stays.

When Indiana's Holiday World opened its Splashin' Safari water park in 1993, the theme park was drawing about 330,000 guests a year. President Will Koch considers it the best investment that his family-owned park has made. This year, thanks to a 14% spike in attendance, Holiday World and Splashin' Safari will have served 880,000 guests.

A couple of hours away, Paramount's Kings Island had its water park undergo an extreme makeover. When the Viacom-owned (NYSE:VIA) attraction realized that it could improve on its original water park, it turned to its growing fleet of Internet-enabled guests to help influence the expansion's direction.

Last year the company contacted pass holders and website visitors who had opted to participate in online marketing research. It also handed out business cards to interested day guests. Then the company turned to Texas-based Inquisite to create an Internet survey to gauge which amenities its patrons wanted to see in the park and what the ultimate theme should be.

Crocodile Dundee's Boomerang Bay Resort was the result of thousands of survey participants favoring a tropical theme after considering other possibilities like a beach boardwalk or a musically intensive MTV motif. Guests wanted cabanas, family change rooms, and lounge chairs with bartending service. They got it.

Perhaps the most promising endorsement of Holiday World and Kings Island's dedication to their water parks is that they ranked second and fifth, respectively, in Amusement Today's Golden Ticket awards for its "Best Waterpark" category. They beat countless stand-alone water parks, which is an impressive feat since these two watery escapes are actually provided for free to park guests.

Not every amusement park operator follows that approach. Disney (NYSE:DIS) has two water parks in its massive Florida resort, and each one is a separate, gated attraction. Cedar Fair (NYSE:FUN) goes park by park, as its flagship Cedar Point and year-round Knott's Berry Farm charge a separate admission for its adjacent Soak City parks, while some of its smaller properties like Dorney Park include the water park for free. Six Flags (NYSE:PKS) also has freestanding locations along with others within existing thrill parks.

That doesn't mean that rolling out a Slip 'N' Slide that empties into a plastic pool will win guests over. It has to be done right. While Kings Island Manager of Marketing Communications and Guest Experience Jeffrey Siebert can't discuss actual attendance figures, he does credit the higher guest satisfaction at Boomerang Bay with spurring advance pass sales for the 2005 season.

At Holiday World, where 70% of the park guests take advantage of Splashin' Safari, expanding the water park has simply become a way for Koch to grow the capacity of the fast-growing attraction.

"We figured adding a water park would make us more sensitive to the weather," Koch explains. "It wound up having the opposite effect, as having a water park and a theme park expanded the range."

Guests who may have written off the theme park experience on a hot day now justify a visit to Holiday World for Splashin' Safari. On a cold day, the nippy timber goodness of the park's two wooden roller coasters will win over the swimsuit crowd.

Living in a world made up mostly of water surfaces, in bodies full of water, it's about time to see amusement parks coming around.

What is your favorite water park? Will a water park influence your decision to visit one amusement park over another? Is it too late to check out our Travel Center to take advantage of the park season coming to a close? All this and more in the Roller Coaster Loving Fools discussion board. Only on

Longtime Fool contributor Rick Munarriz used to think that swimming like Patrick Duffy's character in Man From Atlantis made him go faster. He knows better now. He owns shares of Disney and Viacom as well as units in Cedar Fair.