Strangely enough, EFFY is not a recommended store, even when they have a shop onboard. Because they will not pay a kickback to the cruise line. They are an American company, all merchandise is made in New York, so you don’t pay duty on it, even if you buy on the ship or in Mexico, etc.
Now as to getting a whale tail pendant, I recommend you stop into all of the jewelry stores you pass, as many give out free gifts, and I have at least one silver whale tail…. EM