Movie I remember far back in childhood

So as I said in the title, this movie is one I remember far back in my childhood and I only remember a short scene from it.
Though, in terms of genre I guess it’s an adventure one and probably about magic or a tale or something. I’m not really sure.

The scene is that an old-looking woman swims underwater towards a boat where a young woman and man were talking. She either causes the boat to capsize or grabs the woman pulling her underwater.
Then they both look at each other as if they communicate and say something while people above water are trying to save the young woman. Finally they throw something underwater and the woman grabs it to resurface.