More

common

Less

common

Jellyfish

Microorganisms

E. coli

Staphylococcus aureus

Sea Lice

Salmonella

Vibrio

vulnificus

Stingrays

Sea urchins

Sand flies

Catfish

Stinging coral

Sand Fleas

Sharks

Note: Animals are not drawn to scale.

Microorganisms

Sea urchins

E. coli, norovirus

and Cryptosporidium

Staphylococcus aureus and MRSA

Jellyfish

More

common

Less

common

Salmonella

Vibrio vulnificus

(a.k.a. flesh-eating bacteria)

Sea Lice

Stingrays

Stinging coral

Catfish

Sand flies

Sand Fleas

Sharks

Note: Animals are not drawn to scale.

Microorganisms

Staphylococcus aureus and MRSA

E. coli, norovirus

and Cryptosporidium

Sea urchins

Jellyfish

More common

Less common

Salmonella

Vibrio vulnificus

(a.k.a. flesh-eating bacteria)

Sea Lice

Stinging coral

Stingrays

Catfish

Sand flies

Sand Fleas

Sharks

Note: Animals are not drawn to scale.

Note: The order below is very subjective, as data is spotty and numbers vary by beach and by year.

Microorganisms

Effects range from annoying stomach trouble to life-threatening infections

You are more likely to be attacked by a microscopic marauder than by anything with teeth or a stinger. Some bacteria, viruses and parasites survive and even thrive in warm, salty environments.

Avoid ’em: Keep perishable food cool. Don’t swim at the beach if you’re sick or if you have an open wound or a weakened immune system. Don’t swallow seawater, don’t put your hands in your mouth after touching sand, and shower after you leave the beach. You can check water quality reports here. (Warning: The wonky interface requires a bit of patience.)

Jellyfish

All stings hurt; some can be deadly

The oceans contain thousands of types of jellyfish, ranging from one-millimeter specks to giants with tentacles more than 100 feet long. Stings are common: According to a 2008 National Science Foundation report, about 500,000 people are stung in the Chesapeake Bay every year and another 200,000 in Florida.

Avoid ’em: Keep an eye out for jellyfish in the water, and definitely don’t pick up that colorful, balloonlike thing on the sand — it could be a venomous jellyfish cousin called a Portuguese man-of-war. If you’re stung, rinse with seawater and remove spines with tweezers or the edge of a credit card. Contrary to that “Friends” episode, urinating on a jellyfish sting can make it worse.

Sea lice

Irritating rash is seldom harmful

Sea lice are not insects but baby thimble jellyfish. They ride warm ocean currents to tropical beaches such as in Florida and the Caribbean and get trapped in swimmers’ suits or hair. The friction causes their stinging cells to fire. The result is “seabather’s eruption,” an extremely itchy, acnelike rash.

Avoid ’em: Don’t swim in a billowy T-shirt, which can easily trap sea lice. After swimming, remove your suit and shower as soon as possible.

Stingrays

Injuries are very painful but rarely fatal

Signs that tell waders to do the “stingray shuffle” are not a ploy to make tourists look silly. These shark relatives often lie in the sand in shallow water along nearly all U.S. coastlines. Startling or stepping on a stingray can trigger its self-defense mechanism: in many species, a nasty, serrated, venom-injecting tail. About 1,500 people are injured by stingrays in U.S. waters every year, and the attacks are very painful. One or two people die per year when a barb pierces the chest cavity.

Avoid ’em: Shuffling carefully into the water one foot at a time creates gentle vibrations that alert stingrays to your presence. A sting probably requires a trip to the local emergency room.

Sand flies

Bites are similar to mosquito bites

Sand flies live in sandy areas (including deserts) and feed on their hosts’ blood, leaving painful, itchy welts and sometimes spreading parasites and disease. They are about one-third the size of mosquitoes and are most active from dusk to dawn. (Other biting beach critters include horseflies, gnats and midges.)

Avoid ’em: If you’re in an infested area, wear insect repellent that contains permethrin, and keep skin covered. If a beach insect bites you, wash the spot as soon as you can, apply an ice pack to reduce pain and swelling, and try not to scratch.

Sea urchins

Risks include infection and adverse reaction to venom

These relatives of starfish and sand dollars sometimes live in shallow water on rocky or sandy shorelines. Long spines cause easily infected puncture wounds; venom-injecting small spines cause a burning sensation.

Avoid ’em: Watch where you step in shallow water. If you are stung, remove large spines, try to shave small ones off with a razor, and soak your foot in hot water with Epsom salt to help dissolve spines that remain. Depending on your body’s reaction, you may need medical care.

Stinging coral

Cuts can take a while to heal

Most corals are made up of thousands of individual polyps. Some have sharp skeletons and tentacles with nematocysts (stinging cells) that immobilize prey. Some stinging corals are not corals at all — venomous fire corals, for instance, are hydrozoa, related to jellyfish and anemones. And some sponges sting as well.

Avoid ’em: No matter how pretty it is, be careful to avoid coral when swimming. If it scrapes your skin, its soft body tissue often sloughs off into the wound, causing a painful burning sensation. Stinging cells must be removed. Some people are sensitive to coral venom and need medical attention.

Catfish

Stings are painful and occasionally cause heart and respiratory problems

Catfish are found in waters around the world. Bony, hollow appendages on their dorsal and pectoral fins can inject venom, causing severe pain, infections and occasionally respiratory and cardiac problems. Other fish can sting as well, such as the invasive lionfish.

Avoid ’em: Unless you are pulling one off a hook, you are very unlikely to get stung by a catfish. If you do, immerse the affected area in hot water to ease the pain.

Sharks

Shark bites are rare but serious (as if you didn’t know that)

As of June 26, sharks have attacked 53 people worldwide this year, killing five, according to TrackingSharks.com. (Of the 23 bitten in U.S. waters, no one has died.) Florida is always the hottest spot for shark bites, but the creatures roam plenty of other places, too. A 16-foot great white named Mary Lee has been cruising the Mid-Atlantic lately.

Avoid ’em: Swim close to shore, during daylight hours, and preferably in groups. Don’t get into the water if you’re bleeding or wearing shiny jewelry, as both scream “prey!” If you see a shark, don’t flail but do leave the water as calmly as you can.

Sand fleas

Harmless crustaceans get a bad rep

These pale, clawless crustaceans don’t attack humans, but we included them because people incorrectly use the name “sand flea” to mean sand flies and other biting insects. For instance, the Chigoe flea is often called a sand flea, and it can burrow into your skin and lay eggs. (Icky story here.) Fortunately, Chigoe fleas are rarely found in North America.

Avoid ’em: No need to avoid the crustaceans, which are often a couple of inches long and make pretty good bait. But if you’re barefoot in an area known to have Chigoe fleas, inspect your feet for tiny black spots. Better yet, wear shoes.

Sources

Kelly D. Goodwin, environmental molecular biologist at the National Oceanic and Atmospheric Administration; Florida Department of Health; Florida Museum of Natural History; Orkin; FoodSafety.gov; Centers for Disease Control and Prevention; Washington State Department of Ecology; Journal of Research in Medical Sciences; Environmental Protection Agency.

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