Found a unique shell on my last vaction to Cuba.

[stephanbakir]

I found this diving in Cuba, I've never seen anything like it so wouldn't mind some help identifying it.
Sorry for picture quality my camera is on the verge of dieing.
The shell looks like a tube slide in an amusement park, at no point does one "tube" touch another, it spirals down to a point. If you want i can try and get better photos.