The Barbie Adventure VII: Barbie Fairytopia: Mermaidia

The Equestria Girls make their return to Fairytopia, to Elina's delight. But the eight girls barely get any time to reconcile and fly around (as in their last Fairytopia adventure, they had gotten wings) when they run into a sea butterfly, who has terrible news: Prince Nalu of Mermaidia has been kidnapped by Laverna's fungi! Laverna herself, who had been banished to the Bog of the Hinterlands, was trying to get her fungi to find the immunity berry, which is said to protect you from all magic in the past, present, and future. And they need Nalu to find it. And if Nalu doesn't give them the berry, Mermaidia will be poisoned until no life in the oceanic world exists.
Elina and the Equestria Girls quickly go to try and save Nalu, where they find the mermaid Nori, who's not interested in helping these girls out at first. But eventually, all nine of them track down the Oracle Delphie, who tells them how to find Nalu: go to the bottom of the Depths of Despair and find the Mirror of the Mist, which would help them find his location.
However, there's a price involved should Elina and the Equestria Girls go down there.
In order to find the strength to get to the bottom, they'll have to give up their wings--and their magic--in order to rescue Nalu and prevent Laverna from getting the immunity berry.
Can they do it?
Or is Mermaidia and all of Fairytopia doomed?