Here is an image I created in Raja Ampat one evening while sweating through my sheets on the MV Palagian (that's another story I posted on wetpixel's travel section)
I first took a series of 9 images at 3/4 EV of a sunrise and combined them into an HDR image, then tonemapped the HDR and saved the result as a TIFF file so it was usable. The image below is a re-creation as the tonemapped HDR is 32mb, even as a small jpeg.
I then found an image of a coral head, made the color space, size and bit depth the same as the tonemapped TIFF file, then added the coral image as a layer onto the sunrise file.
I then created a mask in the first image and "painted" the corals into the clouds using a black brush. If I made a mistake such as overshooting a cloud, I would use a white brush to hide that section of the layer (black reveals, white conceals).
I then reduced the opacity of the corals until I got the feel I wanted.



