Jesus said, If one causes one of mine to sin, it is better to have a millstone around his neck and he be cast into the sea. The sea is the sea of iniquity and the sea of disbelievers out side the church. It means that one that caused one of his to sin should be cast out of the church and never rise up above them. If you take the hand of Jesus you can stay above the sea but if you hav e a millstone around you neck, the sea is where you will remain.