What is the narrator point of view in the novel, The Infinite Sea?

The point of view throughout most of this novel is first person, but the narrator varies between several of the protagonists. There are also a couple exceptions where a third-person narrator steps in to tell part of the story. The novel is divided into eight specific parts, and this is also how the narration is separated. Ringer is the narrator in Parts 1 and 7, while Cassie narrates Parts 2, 5 and 8. Evan narrates Part 3, and Parts 4 and 6 are narrated by a third-person narrator who focuses on Poundcake's perspective. All points of view that are used are limited with the narrators only being able to share their own perspectives.