Did you create the name, or did you come across it in your research? If you came across it in your research, what culture / ethnicity does it come from? Is there a story associated with it?
I'm not drawn to the sound of "SELL-kee," and the spelling Selkie looks more like a nn than a formal one. But I could be persuaded to like it with more information. (For me, the fun of names are the associations they conjur up. Created names lack anything to hold onto.)