Havasupai is the name of an Indian tribe who live on a reservation in a canyon that connects to the Grand Canyon. The word Havasuapi means "people of the blue-green water". Often the entire area is just referred to as Havasupai as well. The Havasu Creek runs through the reservation and over several well-known (and photographed) waterfalls. The water actually originates from underground springs and so is a constant 70F temperature year/round. The distinctive color is from a high concentration of lime.
To visit the reservation these days you need permits which are sold on the internet in 3-day chunks, and are very hard to obtain because of its popularity. Day hikes are not allowed. It's about 10 miles from the trailhead to the campground which is where the two most famous falls are located. You can camp in the campground or potentially score a room in the small lodge. We made the trek and camped there for three chilly nights a couple of weeks ago. Even though this place has been photographed to death, it is a place of incredible beauty and tranquility and still a great place to visit. This has been a bucket-list item of mine for many years, and perhaps yours as well if you haven't already been there.
Here are some shots of two iconic waterfalls there taken at night under an almost-full moon.
Havasu Falls in the moonlight
6 Havasu Falls during the day (with a 10-stop ND filter to slow the shutter)
7 Mooney Falls under moonlight, with a Moonbow!
9 Mooney Falls during the day (no ND filter)