Wikipedia
The Apotamkin (also spelled apotampkin) is a creature in Native American mythology. One interpretation of Apotamkin is that it is a myth used to instill fear into children to keep them from venturing into areas alone and without parental guidance.
The Apotamkin was referenced in the popular movie Twilight, spelled as "Apotampkin." It can be spelled either way.
It is often called a "vampire" by non-Native Americans, especially since it was named in the above movie, but in Maliseet and Passamaquoddy legends it is unrelated to vampires. Rather, it is a giant fanged sea serpent that lives in the Passamaquoddy Bay and pulls people in to eat them, particularly careless children. It is said to have long red hair, and in some versions it was a human woman before being changed into a serpent.