Jellyfish at Port Aransas Beach: Species, Safety & Flags

Port Aransas, on Mustang Island along the Texas Gulf Coast, sees seasonal jellyfish influxes—especially late spring through early fall when water temperatures exceed 75 °F (24 °C) and onshore winds push plankton blooms (and their predators) toward the surf zone.

Common Species

• Moon Jelly (Aurelia aurita) – translucent, saucer-shaped, mild sting; most frequent.
• Sea Nettle (Chrysaora chesapeakei) – amber bell, long oral arms; moderate sting, common summer.
• Brown Jelly / Cabbage Head (Stomolophus meleagris) – firm, brownish bell, no tentacles; sting negligible but dense swarms impede swimming.
• Portuguese Man o' War (Physalia physalis) – not a true jellyfish; blue float, 30-ft tentacles; severe sting. Rare but appears after sustained SE winds.

Beach Warning System

Port Aransas uses the International Life Saving Federation flag system:

• Purple flag – dangerous marine life (jellyfish, stingrays, sharks).
• Red flag – high hazard (rough surf, rip currents).
• Yellow flag – medium hazard.
• Green flag – low hazard.

Lifeguards (Memorial Day–Labor Day, 10 am–6 pm) post purple flags at all access points when jellyfish concentrations warrant.

First Aid

1. Rinse with vinegar (5% acetic acid) – inhibits nematocyst discharge (except for Man o' War—use seawater).
2. Pluck visible tentacles with tweezers/gloved fingers.
3. Immerse in hot water (110–113 °F / 43–45 °C) 20–45 min for pain relief.
4. OTC hydrocortisone, oral antihistamine. Seek ER for systemic symptoms (difficulty breathing, chest pain, extensive welts).

Prevention

• Wear rash guard or full-body stinger suit.
• Shuffle feet to alert buried stingrays (co-hazard).
• Heed purple flags; swim at lifeguarded zones (Horace Caldwell Pier, I.B. Magee Beach Park).