I just decided to play today. This is my husband last summer. I thought his slightly anxious expression as he tries the new to him sport looked like he was being chased by something, so I made it so. I used SuperimposeX to add the shark.
@casablanca I think the trick to blending the photos is to try to keep it simple. I do not use any fancy software. I do it with SuperimposeX on my iPad. The app costs about $5 US and has many tutorials. After you learn to make a mask it is pretty easy after that.