St. Francis Xavier Necklace

Why a crab?
One miracle attributed to Francis Xavier involves a crab. While at sea in a storm, Francis offered God his crucifix as a means by which to stop the storm, and God answered his prayer, but the crucifix was lost in the sea. Upon arriving at his destination, however, St. Francis observed a crab on the shore, bringing him his lost crucifix. You can read the whole story here.