Oh I've visited Fun Valley which is at equal distance from Dehradun(30 Km), Haridwar and Rishikesh and is really nice place to enjoy in water.
Good thing is that even during summers the water is cold and clean enough to enjoy.
Timings
Open throughout the year. It's open time is 9 am to 5.30 pm in summer and 9 am to 4-5 pm in Winters. During winter water park will not be available. But other Coaster, Go karting etc will be.
