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.
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City officials say it happens about every three years.