that's not easy for me but I will let the element of water be my guide for a while.
This is my digital entry for the Three Muses Challenge this week (Water). I used a personal photo of a waterfall from a Yosemite trip a few years back, zoomed in to create the background and multiplied the layer for depth. Mermaid is from Dover (Rackham) and from her scales I made some rock-like elements . Gradient filters added in Photoshop.