The second one with the picture of the moon and the beach ties 'Selkie Moon' and the paradise theme together. Also looks more mysterious / dangerous than the first illustration. Having the extra info is also good.
I voted for the first image, because it looks less cheesy, but the second cover conveys the split of the heroine and more of the tension of the story. Depends on your audience. I think the second design tells more but the image of the first is more hip and current.
I think the second cover shows the idea of paradise and the two pictures of the girl show safety and fear.
I think the second cover, which I voted for, is the most commercial. i.e. most likely to entice people to buy. But I still like the original cover for its own sake and think it is the most interesting artistically.
I don't think the first cover is particularly mysterious and feels more like a cover for general fiction published in the 80s (apologies for the bluntness, but this is obviously just one person's opinion). In contrast, the second is both dark and intriguing, and I'd definitely go on to read the blurb.