Minecraft hidden diamond armor set can't find it?

I have a Xbox 360 and there is supposedly a chest underwater by a castle which I can't find at all. They say it's in the tutorial world. But I can't find this castle at all I have searched high and low. They said to stand high on the castle tower and look down there is a 1x1 hole thats lit by glow stone. I have the arcade minecraft if that makes a diff. And I have update tu20 if that helps. Can someone please tell me if they patched this. Or if they didn't can you please tell me how to get to the castle. And also there is supposed to be switches on the minecraft sign on the sides. But there is no switches. Its supposed to open a neither portal. Is this all bs or is it legit. And if the castle exist can some one please post the coords. I know this crap is old but I just got minecraft. Thanks…

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