What do sea shells symbolize?

I was in columbia for vacation when i found all these little spiral shells along with other shells but they are quite pretty so when i got myself into a long distance relationship i made us these little charms with them and they are quite cute, but the point is i want to send him a little note about what seashells symbolize. love wise that is. I heard a couple whispers of what they mean but i need some more info :) thanks. I really appreciate it.