And there's a few Sigur Rós songs as well. Apart from the new stuff, Kjartan Sveinsson added some familiar tunes. One song in particular plays an important part in the plot. Ondine sings it to the fishes, while being all mystical and mysterious. After all, what else would mermaids sing? The fisherman thinks it's a magical sound, proof of her being from another world. Then Sigur Rós appear on TV singing it, making him wonder if it really is a selkie song. 'That song, it's real', 'Of course it's real, it's Sigur Rós' - this is good dialogue. A film that hinges on a Sigur Rós song? This can only be a good thing.