A box jellyfish advisory is in effect today and Friday.

An updated count of box jellyfish on O'ahu will be available later today.

Last month, about 1,000 of these marine creatures washed up on Makaha Beach Park, with another 500 at Poka'i Bay in Wai'anae.

About 400 box jellyfish came ashore on beaches from Ala Moana to Hanauma Bay.

Box jellyfish come into shallow waters at night during their spawning, which takes place eight to 10 days after the full moon.

Anyone who is stung and experiences difficulty breathing, muscle cramps or spasms or persistent pain should seek medical help.

For the latest information about ocean conditions, call 922-3888, ext. *51, or visit www.hawaiibeachsafety.org.