The waters around Guernsey are home to various jellyfish species. Some are harmless, while others can cause painful stings. Knowing what to expect and how to respond to jellyfish encounters can help swimmers and beachgoers stay safe.
Barrel Jellyfish
(Rhizostoma pulmo)
- Appearance: Large, dome-shaped bell that is white or pale blue. Thick, frilly arms with no visible tentacles.
- Size: Can grow up to 1 meter in diameter.
- Danger Level: Low. Stings are mild and generally harmless.
- First Aid: Rinse with seawater, apply a cold compress if necessary.
Moon Jellyfish
(Aurelia aurita)
- Appearance: Transparent, circular, flat bell with four purple or pink rings in the center.
- Size: Typically 25-40 cm in diameter.
- Danger Level: Low. Stings are mild and generally cause only slight irritation.
- First Aid: Rinse with seawater and apply a cold compress for any discomfort.
Compass Jellyfish
(Chrysaora hysoscella)
- Appearance: Bell marked with dark, V-shaped lines resembling a compass. Tentacles are long and yellowish-brown.
- Size: Up to 30 cm in diameter.
- Danger Level: Moderate. Stings can cause pain, redness, and swelling.
- First Aid: Rinse with seawater, apply heat (e.g., hot water), and seek medical help if necessary.
Blue Jellyfish
(Cyanea lamarckii)
- Appearance: Bell is blue or violet, with short, relatively thick tentacles.
- Size: Typically 30 cm in diameter.
- Danger Level: Moderate. Stings can be painful but are usually not dangerous.
- First Aid: Rinse with seawater and apply heat to reduce pain. Antihistamines can help with itching.
Mauve Stinger
(Pelagia noctiluca)
- Appearance: Small, with a pink or mauve bell and long, thin tentacles. Sometimes bioluminescent (glows in the dark).
- Size: Around 10 cm in diameter, with tentacles up to 3 meters.
- Danger Level: High. The sting is painful and can cause burning, welts, and even nausea.
- First Aid: Rinse with seawater, apply a cold pack, and avoid scratching. Seek medical help for severe reactions.
Lion’s Mane Jellyfish
(Cyanea capillata)
- Appearance: Large, reddish-brown to orange bell with long, flowing tentacles.
- Size: Can grow up to 2 meters in diameter, with tentacles reaching over 30 meters.
- Danger Level: High. Stings can cause intense pain, burning, and skin irritation. In severe cases, it can lead to breathing difficulties.
- First Aid: Rinse with seawater (not fresh water), apply cold packs, and seek medical attention for severe reactions.
Portuguese Man o’ War
(Physalia physalis)
- Appearance: A floating, balloon-like structure in blue, purple, or pink, with long trailing tentacles beneath the surface.
- Size: The float can be up to 30 cm, but tentacles can extend to 30 meters.
- Danger Level: Very High. The sting is extremely painful and can cause severe symptoms such as difficulty breathing, chest pain, and, in rare cases, death.
- First Aid: Do not touch. Rinse with seawater and apply heat, and seek medical attention for severe reactions.
What to Do if You Encounter a Jellyfish
Jellyfish are a common part of Guernsey’s marine ecosystem, and understanding how to respond to stings is essential for safe swimming.
- Do Not Use Fresh Water: Always rinse with seawater to prevent more venom from being released.
- Apply Heat: If stung, apply warm water to alleviate the pain (except in the case of a Portuguese Man o’ War, where cold compresses are recommended first).
- Seek Medical Help: If symptoms such as breathing difficulties, severe pain, or allergic reactions occur, contact emergency services immediately.
Reporting Jellyfish Sightings
You can help keep other swimmers safe by reporting sightings of jellyfish, particularly more dangerous species like the Portuguese Man o’ War or Lion’s Mane. Early warnings can prevent stings and ensure everyone enjoys Guernsey’s beaches safely.