I think, the movie tried to explore the themes: "being yourselves" or "embracing yourselves with all your oddities" or "finding how special you are".
It is an interesting film, but leaves you confused at the end; all because one shot, I think, has gone wrong. The point is, the movie follows a grounded-realistic approach (not a surreal one). So, you expect the movie to give you enough information to build a believable world in which the story takes place. The problem is not with the believability, but with the incomplete information. So, at the end, you are left feeling that there is something missing.
This could have been fixed with the very first shot of the movie, in which it could have shown a new born lying on the beach crying, with no traces of any human around her. This would have raised the question, "who left her there?" or "where did she come from?". As these questions were quite satisfactorily answered in the movie, you would've felt that everything fell in place (including the theme). The parents' characters need a little development though.
