Manta rays appear a few times during the movie, Moana.
Appearance
The manta rays are gray, most of the time, but when Gramma Tala comes back as one, she is blue with designs on her back.
Role in the Film
The manta rays are first seen dancing with Gramma Tala. They are swimming in circles around her. Gramma Tala's tattoo is also that of a manta ray.
When Gramma Tala dies, she comes back as a manta ray. As a manta ray, Gramma Tala guides the way for Moana.
At the end of the film, Gramma Tala swims past the boat in her manta ray form.