Board Thread:General Discussion/@comment-25850402-20150723062747/@comment-24674051-20150724174707

actually, I could see the storm calling being a mermaid magic type thing. Mermaids like to cause havoc with ships in the water, and that would be another way to do that (aside from singing to attact sailors into treachorous rocks).

And the singing was not just Ursula. When Ursula was drawing the Jolly Roger towards the Rocks (Poor Unfortunate Soul), and Hook realized what was going on, he distinctly pointed out that it was MERMAID singing that was the cause. And with his experience in Neverland, I would imagine that he had more than one encounter with Mermaids prior to this.