A lot of water = Standard English, sounds more correct. “There is a lot of water at the water park” Lots of water = Colloquialism, a spoken form usually used to exaggerate the fact that a huge quantity of a given thing exists, not formally correct. “There’s lots of water at the water park”

They are exactly the same when used as the quantity of a noun. I have lots of friends. I have a lot a friends. However, typically only 'a lot' is used to modify a verb. I talk a lot. NOT I talk lots. They travel a lot. NOT they travel lots.

Sebas gave a good answer. Not much of a difference, except „lots of“ is more colloquial, non-standard speech, but many people use it everyday.

No difference.