There are several options for both natural and manmade beaches.
Mt. Olympus Resort has the largest sand beach, which is 16 inches deep and adjacent to Poseidon's Rage, a wave pool that regularly unleashes a 9-foot wave.
Adventure Lagoon at Chula Vista Resort also has a sand beach, which is smaller than Mount Olympus and more suitable for younger kids. It's outfitted with beach chairs, a tiki bar and private cabanas.
Lake Delton, itself a manmade lake supplied by Dell Creek, is a whole lot spiffier than it was several years ago. After heavy rains caused a dike to fail and the lake to drain in 2008, the shorelines were scraped before the lake was refilled. Beaches of note: Baker's Sunset Bay Resort, the Thunderbird Resort and Moonglow Vacation Homes.
The Wisconsin River has its own sandy beaches, a bit more rugged than those on Lake Delton. Here's where you'll find the beaches: Holiday Shores Camp-Resort, Cedar Lodge and Settlement and River's Edge Resort. New this year is Newport Park, which has its own beach, fishing pier and a boat launch that provides access to the Lower Dells of the river.
The essentials: Some Dells water parks, including Mount Olympus, include admission to the park in the price of lodging. That's a pretty good deal. In late August, I paid about $140 per night for a room for two adults and three kids, but by the time we included concession charges (you can pay with a wristband) -- mostly for snacks, taxes and an assortment of fees -- our two-night stay cost more than $600. Prices will be most affordable when demand is lowest, and last-minute deals are often available. During the last week of August, when most Wisconsin children are in school, visitors can land good prices and hop on slides with no lines.