South-shore arrival predictions based on the lunar cycle
South-shore O'ahu · Next warning window
Warning windows tied to the lunar cycle
The lunar-cycle pattern
Box jellyfish arrive on Hawaiʻi's shores in a predictable pattern tied to the lunar cycle. Roughly 8–10 days after each full moon, ocean currents push them toward south-facing shores, particularly Waikīkī, Ala Moana, and Hanauma Bay on O'ahu.
The pattern has been documented over decades by Ocean Safety lifeguards and marine researchers. While south-facing shores see the highest concentrations, jellyfish can appear on any shore given the right wind and current conditions.
Current treatment guidance
Rinse with vinegar to neutralize stinging cells.
Apply heat (hot water or hot pack, 40–45°C / 104–113°F) for pain relief.
Don't rinse with fresh water, don't rub with sand.
Seek medical care for severe pain or reactions.
About box jellyfish in Hawaii
Sting treatment walkthrough
All arrival dates are predictions based on the lunar cycle. Jellyfish can be present any day of the year depending on conditions. Always obey posted warning signs, swim on guarded beaches, and ask a lifeguard about ocean hazards before entering the water.