In the movie Moana she hits her head while trying to escape the thrashing waves. when she wakes up she’s on the beach and has magic water powers.

I believe she is actually dying and everything after that point in the movie is a fantasy in her head as she slowly dies. she knows this deep down and struggles with the concept of death immediately after when her grandmother dies, thus sending her off on a journey to save her people (herself).

she then follows Maui who guides her along to the afterlife (even takes a small detour to the underworld). when she finally meets Te Fiti the goddess is in a state of duality (life and death). only after restoring Te Fiti to her living state does she return to her people where they welcome her back to the land of the living.