Okay, I’m confused! Is this a composite or not?
My first impression was that their heads look too cut out, and I assumed that you had cloned something out of the water behind them. In fact I was so drawn to the heads that I didn’t even notice the dog until I started reading the post. Ebi was asking about halos which I assumed were from the cut out, but then you mention the DOF was f8. So have you masked the couple to adjust the exposure on the rest of the image? Maybe you post the original image?
She appears to have a very flat head whilst he appears to have a perfect circle, and they both have a black out line along their chins.