omg... the urban legend is that it is a superstition. Cause it never was a superstition, hence it is simply an urban legend cooked up by Hollywood and fantasy writers.
If i started my lecture how about i add something. Sailors never thought the earth was flat. This is also an urban legend. Picture this: when a ship emerges from the horizon, can you see the entire ship? No, only the masts. What does this mean? It means that the earth is not flat but rounded. The sailors knew this, it was the clergy that thought otherwise.
Wezqu, you seem like the kind of lad that likes to stick his nose and play the smart guy. Well maybe you are, you got any proof that it was actually recorded that sailors thought it would bring bad luck? If you do, please show us. Otherwise it is not true, and its merely an URBAN LEGEND.