The lighting here is gorgeous! I really like how you've set up the composition, I know she's supposed to be pulling him down but he could just as well be trying to pull her up. It could either be super creepy or strangely hopeful.
This is really well painted and composed, my only beef is her tail is a little irrationally long. There would be too much length to push through the water, and pretty much all of the skinny part beneath the sidefin things is too thin to be of any use. Sorry if it seems overly analytical. I get that way when I'm tired.