A walk along the beach often reveals the translucent, gelatinous forms of stranded jellyfish. These marine organisms, composed of about 95% water, are a common sight, washed up by ocean forces. Knowing how to identify these creatures and understanding the potential risks they pose is important for a safe experience. This guide explains what a washed-up jellyfish looks like, why it is there, and how to safely navigate an encounter.
Identifying Stranded Jellyfish
The appearance of a jellyfish changes significantly once it is no longer supported by water, making it look much different than its swimming form. What was a dome-shaped, often transparent bell collapses into a flattened, amorphous mass on the sand. Because the animal is mostly water, it begins to dry out and lose its structure almost immediately, becoming opaque or milky-white in color.
The bell, which is the main body, loses its perfect umbrella shape and becomes a gelatinous blob. Tentacles and oral arms, which hang down in the water, may be tangled, shriveled, or torn away entirely by the surf. While many common species like moon jellyfish appear clear or pale white, others can display distinct colors, such as the deep purple of a compass jellyfish or the blue-tinged float of a Portuguese man-of-war. As the sun and wind desiccate the organism, it can shrink down to a thin, dry imprint on the sand.
Are Washed-Up Jellyfish Still Dangerous
A jellyfish on the sand should always be treated as a hazard because its stinging apparatus remains active even after the organism has died. The stinging mechanism is contained within microscopic structures called nematocysts, which are non-living, spring-loaded capsules. These tiny harpoon-like threads, filled with venom, are triggered mechanically by contact, not by the jellyfish’s nervous system.
Since the stinging cells are independent of the creature’s life processes, they can continue to fire venom for a significant period after washing ashore. Depending on environmental factors like humidity and sun exposure, the nematocysts can remain functional for hours or even days. Even a fragment of a tentacle can deliver a sting upon contact, meaning any moist or intact specimen carries the risk of envenomation.
Why Jellyfish Wash Ashore
Jellyfish are classified as plankton, meaning they are weak swimmers whose movements are dictated by the forces of the ocean. Unlike fish, they have limited ability to navigate against strong currents, tides, or wind. The primary factors leading to mass strandings are strong onshore winds and specific tidal cycles.
When wind blows consistently toward the shore, it can push entire groups of jellyfish, known as blooms, out of the open water and onto the sand. Specific species, such as the by-the-wind sailor (Velella velella), are especially susceptible because they possess a rigid, sail-like structure that catches the wind, inadvertently propelling them to their demise. Changes in ocean conditions, such as warming waters or rough seas, can also increase the frequency of these stranding events.
What to Do If You Encounter One
The rule when encountering a stranded jellyfish is to avoid all physical contact, even with a stick, because of the retained stinging capacity. Beachgoers must ensure that children and pets are kept a safe distance away from any gelatinous mass. If a jellyfish is spotted, especially a highly venomous species like the Portuguese man-of-war, the sighting should be reported promptly to a lifeguard or beach authority.
If accidental contact and a sting occur, immediate first aid focuses on preventing any remaining nematocysts from firing more venom. The most effective treatment for pain and venom inactivation is immersing the affected area in hot water, approximately 110°F to 113°F (43°C to 45°C), for 20 to 45 minutes, or as hot as can be tolerated without scalding.
First Aid for Stings
- Rinse the affected area thoroughly with seawater, not fresh water, as fresh water can cause unfired stinging cells to discharge.
- Carefully remove visible tentacles using tweezers or a gloved hand, avoiding scraping the skin, which can also trigger stinging.
- In certain locations, applying vinegar may be recommended to help neutralize the sting from specific local species.