There's a movie I remember and I can't find it in Netflix nor a general search on the internet, nor the movie databases on the internet.

It was simply named ISLAND. Not THE ISLAND, or any other word with ISLAND, just ISLAND.

Made sometime in the 1970's, I think. There was a book written first, named ISLAND. It was about some pirates that captured a kid (girl? I think) and took her to this island overrun by pirates, where she/he eventually becomes one of them, I think.