Honolulu lifeguards are warning beachgoers of an influx of box jellyfish at Waikiki and Ala Moana beaches and Nanakuli Beach Park today.
Box jellyfish can cause a painful sting and in some instances an allergic reaction.
The stinging invertebrates are named for the squarish shape of their bell-shaped body, according to the Waikiki Aquarium website. The box jellies usually arrive near shore 8 to 10 days after a full moon, which was Jan. 17.
Lifeguards have posted warning signs at the affected beaches.
Honolulu Ocean Safety recommends beachgoers check with lifeguards on current beach and ocean conditions.