I remember the movie really well honestly. It was in color and I saw it most likely on Sci-Fi, I don’t remember when at all honestly.
There was a group ( I believe 3 or 4) riding a boat much like this http://0.tqn.com/d/powerboat/1/0/_/1/-/-/CoastalFishing-GradyWhite.jpg out in the middle of the ocean. There were at least two males and there was one female, I think only one, but I’m not a hundred percent sure. The female was definitely in some sort of relationship with on of the males, OR he had major feelings for her. I think they were vacationing, you know just sailing. They see an island and then they found some guy who was a castaway not too far from the island, took him aboard and he was like really out of it and the boat got stuck on(or pushed into by the monster, I don’t quite remember) the rocks and the boat was stranded.
Somehow somebody goes up to the island( I don’t remember if they swim or what happens) and they find out the inhabitants( some people who are like… A cult or a race of just hostile humanoids I don’t remember). I THINK this was when they take the woman. The others go back to the boat and then the Stranger comes to the island again to help the Guy who was in love with/in a relationship with the woman who was taken. Stranger is killed unfortunately(I liked him:( ) anyways. The remaining guy finds the woman, she is in a room or building filled with the Hostile Humanoids and they are getting ready to like sacrifice her into this whirlpool for the sea monster(never knew what it was honestly). He saves her by fire or something like that. Then she’s all like ‘no i must go’ and then she voluntarily sacrificed herself and that’s it.
I think it ended with like what would be her view inside the whirlpool as she drown.
The weather was really dreary on the island, I THINK the main dude wore glasses. It was like a horror/thriller type thing and it was surprisingly good. Definitely a movie though, not a show or a special.