Authorities posted photos to the city's Facebook page last Thursday.
The bluish-purple jellyfish are called "velella" or nicknamed "blue sailors." They are not known to sting, but they often travel with stinging Portuguese man-of-war jellyfish.
The sea critters have bodies designed to allow them to sail away from shore.
However, strong winds can catch the fins and carry them onto beaches.
City officials say it happens about every three years.