A box jellyfish advisory has been issued for Waikiki and Ala Moana beaches, in whose waters the stinging invertebrates have been spotted, the City and County of Honolulu announced today.

A common hazard to swimmers and surfers, who can be caught in their tentacles, box jellyfish also wash up on beaches and contact with any part of their bodies, whether alive or dead, whole or in pieces, can result in excruciatingly painful stings and, in allergic people. a deadly reaction such as anaphylactic shock.

Lifeguards at beaches have posted signs warning the public against swimming in jellyfish-infested waters.

Numbers of the floating, transparent jellyfish typically increase between eight to 10 days after a full moon, according to the Waikiki Aquarium box jellyfish calendar, which lists today, the 10th day after the December full moon, as a high hazard day for box jellyfish.

Honolulu Ocean Safety recommends beachgoers visit the nearest lifeguard tower for information on current beach and ocean conditions, and swim at guarded beaches.