STE P BY STE P
1 Water colours
White balance can be off underwater, so shoot in RAW. In Adobe Camera Raw, grab the White Balance tool and click over a point that should be neutral to fix colour casts. Next, open the image in Photoshop and tweak the colours with a Color Balance Adjustment Layer.
2 Tidy the background
Pool markings can be distracting, so remove them for a seamless background. The two tools for the job are the Clone Stamp Tool and Spot Healing Brush. Both can be set to Sample All Layers, so make your edits on a new, empty layer to preserve the original image.
3 Fix chromatic aberration
Using a housing means shooting through extra glass or plastic, so you might find colour fringing affects edge details in your image. If this is the case, go to Filter>Lens Correction, then use the Manual tab and experiment with the three colour fringing sliders.