It is derived from popular movies and commercials where a character is splashed with water to accentuate their beauty.
This popular style scene is often known for being replicated in comedies such as Shrek when Puss in Boots dances at the party, he sits back in a lounge chair, pulls a string, and douses himself with water - a reference to Flashdance (1983)
Often times in music videos the scenes will show extremely done up figures that can be considered as splash beauty.
When someone sees an example of splash beauty, they will be unable to have words in awe of the intense beautiful moment. At this moment, the individual may be able to gather the two words "Splash" Beauty" to describe their feeling of an overwhelming burst of intense beauty that has unveiled itself right before their very eyes.