Create and refine a composition with filters and masking tools
Create a new document via File>New>Blank File. In the New window enter the name Mermaid and set the Width to 395mm, Height to 310mm and Resolution to 300 pixels/inch. Click OK.
Now grab the Gradient tool (G). Open the Gradient Editor and set the first colour to #8dbba0,the second colour to #121725, and then click OK. Select the Radial Gradient and drag from the top-right corner to bottom-left corner.
Create a new layer (Cmd/ Ctrl+Shift+N) and name it Water Effect. Grab the Rectangular Marquee tool (M), hold Shift and create a selection. Grab the Paint Bucket tool (G) and fill this with white. Go to Filter>Render>Difference Clouds. Go to Filter>Filter Gallery>Artistic> Plastic Wrap, and set Highlight Strength to 15, Detail to 5 and Smoothness to 10.
Click Cmd/Ctrl+T to adjust the size. Head to Edit>Transform> Perspective, drag the corners to adjust the angle, and then press Enter. Change the blend mode to Overlay and add a layer mask. Open the Gradient tool (G), choose the Black/White preset, set it to Linear and drag up to remove the hard edges.
Place a seabed image. Go to Layer>New Adjustment Layer>Levels and set the inputs to 0, 0.98, 245 and clip the layers. Now go to Layer>New Adjustment Layer>Hue/Saturation. Click Colorize and set the Hue to 155. Saturation to 20, Lightness to -30 and clip the layer.
Go to Filter>Blur>Gaussian Blur and set the Radius to 5 pixels, click OK. Now add a layer mask and open the Gradient tool (G). Choose the Black/White preset, set to Linear and drag down to remove the hard edges.
Create a new layer called Water Reflection. Grab the Rectangular Marquee tool (M) hold the Shift key and create a selection. Go to Filter>Render>Clouds, and again Filter>Render>Difference Clouds. Press Cmd/Ctrl+T to adjust the size and perspective over the Seabed layer.
Hold Shift and select the hair layer and the mermaid. Hit Cmd/Ctrl+E to merge them. Now add a layer mask and grab the Pen tool (P). Select the hip and legs, Ctrl/right-click, choose Make Selection and fill with black.
Place a mermaid tail and hit Enter. Press Cmd/Ctrl+T and choose Warp mode. Drag the handles to create a fish shape and press Enter. Hit Cmd/Ctrl+T, rotate and adjust the size. Drag the scale layer and place under the mermaid.
Go to Edit>Puppet Warp (Elements users go to the Liquify filter). Set four points along the tail, drag the points to create a curve and hit Enter. Now select the mermaid’s layer mask. Grab the Brush tool (B), set Foreground colour to white, change Opacity to 40% and paint around the hip.
Place fin images onto the composition. Adjust the size, and hit Enter. Ctrl/ right-click and choose Rasterize (Elements choose Simplify). Drag the right fin layer over the Scale layer and grab the Eraser tool (E), set Opacity to 40% and rub out to blend. Merge the layers (Cmd/Ctrl+E).
Go to Layer>New Adjustment Layer>Hue/Saturation. Set the Hue to 72, Saturation to 15, Lightness to -10 and clip the layer. Hold Shift and select the mermaid, the adjustment layer and the tail, and then merge them. Create a Neutral layer (hold Opt/Alt while clicking on Add New Layer). Grab the Dodge and Burn tools and add shadows and highlights.
Place fish and reefs around the composition. Press Cmd/Ctrl+T to resize and rotate. Hit F5 and click the Brush Preset palette. Load brushes a bubble brush. Save a version of your image as a JPEG, reopen it, and then apply a vignette effect (Filter>Lens Correction).