The most likely culprit is a jellyfish, but Florida waters are home to several animals that sting, scrape, or puncture unsuspecting swimmers. Figuring out what got you comes down to three things: what the pain felt like, what your skin looks like now, and where on your body it happened. Here’s how to narrow it down.
Jellyfish: The Most Common Sting
If you felt a sudden burning or stinging sensation while swimming and now see a line of raised red or purplish bumps on your skin, a jellyfish is the most probable cause. Florida’s Atlantic and Gulf coasts host several species, including moon jellyfish and Atlantic sea nettles. The sting pattern typically follows the path of the tentacle that touched you, leaving a streak or whip-like mark rather than a single spot. These welts can last one to two weeks, and blisters or deeper sores sometimes develop.
For most jellyfish stings in Florida, rinse the area with seawater (never fresh water, which can cause unfired stinging cells to release more venom). A baking soda slurry can help prevent additional stinging-cell discharge from sea nettles, which are common along the Atlantic coast. Cold packs applied after rinsing can reduce pain.
Portuguese Man o’ War
The Portuguese man o’ war is not technically a jellyfish but a colony of organisms that floats on the surface with a blue or purple gas-filled bladder and long trailing tentacles. If you were stung by one, you likely noticed intense, immediate pain and a pattern of raised red, brown, or purplish welts that can look more severe than a typical jellyfish sting. The tentacles can reach several feet, so the sting marks may cover a large area.
Man o’ war stings respond well to vinegar, which helps prevent remaining stinging cells from firing. Hot water immersion, around 109 to 113°F for about 20 minutes, is also recommended for pain relief. You can sometimes spot man o’ war washed up on the beach, which is a clue that they’re in the water nearby. Their tentacles can still sting even when the animal is dead on the sand.
Sea Lice (Seabather’s Eruption)
If the rash showed up under your swimsuit rather than on exposed skin, you’re almost certainly dealing with seabather’s eruption, commonly called “sea lice.” This is caused by tiny, nearly invisible larvae of certain jellyfish species that get trapped between your clothing and your skin. Friction and pressure from waistbands, straps, and suit edges trigger their stinging cells.
The rash appears as scattered itchy red bumps, sometimes progressing to small blisters or pustules, concentrated beneath the bathing suit. The itching can be intense. Sea lice are most common in May and June along Florida’s coast, especially in South Florida. You may not feel anything in the water and only notice the rash hours later. Over-the-counter hydrocortisone cream and antihistamines help with the itching, and the rash typically resolves within a week or two.
Stingray Strike
If the pain hit your foot or ankle like a sharp stab and the wound is jagged or bleeding freely, a stingray is the likely cause. Stingrays bury themselves in shallow sandy bottoms, and when someone steps directly on one, the ray whips its barbed tail upward. The pain is immediate and severe, often reaching peak intensity within 90 minutes and lasting anywhere from six hours to several days. Nausea, weakness, and anxiety commonly follow.
The wound edges may appear discolored, and pieces of the stingray’s barb sheath can remain in the wound. Stingray injuries are different from jellyfish stings in that they cause a puncture or laceration, not a surface rash. These wounds need thorough cleaning and often benefit from medical attention because of infection risk and the possibility of retained barb fragments.
Fire Coral
If you were snorkeling, diving, or wading near a reef and brushed against something that looked like a yellowish-green or brownish branching structure, fire coral is a strong possibility. Despite the name, fire coral is more closely related to the man o’ war than to true coral. Contact produces an immediate burning sensation that can last several hours, followed by a skin rash that appears minutes to hours later.
The rash usually fades within a day or two but can reappear days or even weeks after the initial contact. If the coral scraped or cut your skin in addition to stinging it, the injury can be more serious. Fire coral venom can cause tissue damage at the edges of an open wound, so lacerations from fire coral deserve medical attention.
Sea Urchins
If you stepped on something and now have dark spots or visible spines embedded in your foot, you likely encountered a sea urchin. The pain is sharp, localized, and gets worse when you press on the area. You may see slight redness and swelling around each puncture point. Some species carry venom that intensifies the burning and inflammation and can cause numbness or tingling that radiates outward from the wound.
Visible spines sticking out of the skin should be carefully removed. Pulling them straight out is important because the spines are brittle and can snap if twisted or squeezed too hard. Broken fragments left in the skin can cause ongoing pain, granulomas (hard lumps), or infections weeks later. If a spine breaks off beneath the surface, it doesn’t necessarily need surgical removal unless it continues to cause symptoms.
How to Tell What Got You
- Line of raised welts on exposed skin: jellyfish or man o’ war
- Itchy rash under your swimsuit: sea lice
- Burning rash after touching a reef structure: fire coral
- Jagged bleeding wound on foot or ankle: stingray
- Puncture wounds with dark dots or visible spines: sea urchin
Signs That Need Emergency Care
Most marine stings in Florida are painful but not dangerous. However, some people develop severe allergic reactions. Get emergency help immediately if you or someone with you develops difficulty breathing, swelling of the lips or tongue, hives spreading beyond the sting site, dizziness or confusion, a weak pulse, or loss of consciousness. These are signs of anaphylaxis, which can progress rapidly from mild swelling to life-threatening shock.
Stingray wounds to the chest or abdomen, though rare, also require immediate emergency care regardless of allergic symptoms.
Preventing Stings Next Time
The simplest prevention for stingray injuries is the “stingray shuffle.” Instead of stepping normally when you walk into the water, slide your feet along the sandy bottom without lifting them. This creates vibrations that stingrays can detect, giving them a chance to swim away before you’re on top of them. If your foot bumps the side of a buried ray rather than landing on it, the ray is far more likely to flee than strike.
For jellyfish, check the beach flag system before getting in the water. A purple flag means potentially dangerous marine animals have been spotted in the area. Purple flags can fly alongside other colored flags indicating water conditions. Wearing a rash guard or full wetsuit reduces exposed skin and can also help prevent sea lice, since the larvae are less likely to get trapped and compressed against your skin when clothing fits snugly without loose waistbands or edges.