But a waterpark is a whole other story!

Two options for Turtle Splash Water Park in West Chicago:

$10 for water-park admission for two (up to a $16 value)
$16 for water-park admission for four (up to a $32 value)

Limit one per person; additional two as gifts.

Barefoot Bay Family Aquatic Center in Mundelein has an admission package for two for $13 on livingsocial. Package includes lazy river, three water slides, water climbing wall and  dedicated tot area. Parking and use of lounge chairs is free. Limit three vouchers per person.