Seashell Mystery

This may not be much of a mystery to most but when you see something like this in my line of work it makes you scratch your head. This is a buoy that marks one of my crab pots that I found with a seashell perfectly implanted in the foam. I only have two possibilities that I could imagine. This first, most reasonable, is that a sea gull was carrying this far above when it dropped and landed with its point perfectly aligned to the buoy. Hard to believe but possible.! That foam is pretty hard! The second one is that someone decided (for fun?) to press this shell into my buoy. Why anyone would do this I will never know. It was in a very remote area. Anyone have any better ideas or stories for this unexplained sight?