A tripod, strong neutral density filters and water... what a trifecta!
I started playing with waterfalls on a trip to Hawaii in 2008- those are the first 3 here.
More recently, I shot a poolside LE and then the ocean in Aruba.
The fountain shot was taken in Paris this past June
The remaining images were from a wonderful, but beastly hot, Long Exposure Workshop in South Carolina this past August.