Sting treatment, prevention, and which beaches to avoid
Call 911 immediately for any of the above. Do not wait.
The Portuguese man-o-war (Physalia physalis) is not actually a jellyfish — it's a colonial organism made up of multiple specialized polyps. It gets its name from its gas-filled float (pneumatophore) that resembles an old Portuguese warship under sail. The float is typically blue-purple and 2–6 inches long. Tentacles can trail 30–100 feet below the surface, though in Hawaiian waters they're typically shorter.
Man-o-war cannot swim — they drift with wind and currents. When trade winds blow from the northeast, they push man-o-war toward Hawaiʻi's windward shores. They are most visible on the surface but their tentacles extend deep and are virtually invisible in the water.
Get out of the ocean. More tentacles may be nearby and continued contact worsens the sting.
Use a credit card, shell, or stick to scrape off tentacles. Never use bare fingers or rub the area — this embeds more nematocysts.
Fresh water causes unfired nematocysts to discharge, worsening the sting. Use ocean water or saline to rinse.
Hot water immersion (as hot as tolerable, not scalding) or a heat pack for 20 minutes significantly reduces pain. This is more effective than ice.
Ibuprofen or acetaminophen for pain. Lidocaine spray (available at dive shops) helps. Hydrocortisone cream for itching. Antihistamine for swelling.
Watch for signs of allergic reaction. Welts and pain are normal; difficulty breathing is an emergency.
Beaches facing northeast are most vulnerable when trade winds are strong:
Free water quality and ocean safety alerts for your Hawaii trip.
Safe to Swim Hawaii is an independent passion project. This guide is for educational purposes only — it does not replace professional medical advice. Seek medical care if symptoms are severe after a sting.
When in doubt, don't go out. 🤙