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March 2002 Vol. 28, No. 3   RSS Feed for Undercurrent Issues
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Diving in Florida or the Caribbean This Spring?

fear this . . .

from the March, 2002 issue of Undercurrent   Subscribe Now

Whatever fears you face when you go diving in new waters, it’s unlikely that “sea lice” is among them. However, given the easy waters of the Caribbean, sea lice are among your worst enemies.

Consider what Mike Stevens of Atlanta experienced last May at the Brac Reef Resort on Cayman Brac. “Great resort, laid back, attentive staff, but this is big one: thimble jellyfish. The larvae of the thimble jellyfish, commonly called sea lice, are a serious hazard to the enjoyment of your expensive dive trip. Many divers at the resort suffered. Anyplace water can reach, including under any wetsuit/skin/hood/booties is susceptible to the larvae. My wife and I used full wetsuits and slathered a product called SafeSea on all exposed areas and were not bitten at all. Many divers who did the same thing were bitten. There may be a component of whether or not you are immune to them, something like being immune to poison ivy. The larvae cause dimesized welts, resembling a giant mosquito bite. One guy had them over his entire body, and I cannot imagine the torture he was enduring. Most people had them on their necks, faces and backs. I’m talking some serious looking welts, and lots of them. The dive operators try to take you to sites where there are no obvious jellies on the s u rface (they look like quarter- size brown mushrooms) but people still got bitten. We did not dive the Russian destroyer at all because a mat of billions of TJ’s covered the north side of the island. The Cayman Islands Health Services , Accident and Emergency Department issued a warning while we were there to “not enter the sea unless absolutely necessary.” Not a good thing to hear when you have spent big bucks to get to this paradise.

The larvae cause dime-sized
welts, like a giant mosquito
bite. One guy had them over
his entire body, and I cannot
imagine the tort u re he was
enduring. Most people had
them on their necks,
faces and backs.

Diving with Ocean Frontiers on Grand Cayman the same month, Charles Sanetra (Henderson, NV) said he loved the dive operation but, “Both my wife, myself and others diving on the same boat got stung by the larvae of the Thimble Jellyfish. We were unaware of any preventive actions but knowing how to manage the problem after it occurred would have been nice. We had to see a doctor for my wife’s case as she had a severe reaction.”

What are Sea Lice?

“Sea lice” is a common misnomer for the larval forms of thimble jellyfish. They aren’t lice at all and look nothing like them under magnification. What we’re really talking about is what doctors call “Sea Bather’s Eruption” (SBE), which is caused by pinhead- sized larvae of the Thimble Jellyfish that float near the surface. While they are common in the Cayman islands, they can be found in the waters off Florida, in the Gulf of Mexico and in the wider Caribbean. While they might affect divers from March to August, early April to early June seems to be the peak season.

Don’t be lulled into a false sense of security just because you see no thimble jellies around. The larvae are about before and after the adults have disappeared. While adults may swarm in large numbers and look yucky to dive through, they are much less toxic than their larvae, usually only causing a mild reaction in those with sensitive skin.

Each larva is surrounded by nematocytes, capsule-shaped cells with a trapdoor-like lid. Inside is the mechanism that does the damage—the nematocyst. This stinging organ contains a long, barbed filament that can be propelled into the skin, injecting a mixture of substances that can have direct toxic effects cause immune reactions. The same mechanism enables corals, anemones, hydroids and adult jellyfish to sting. The larvae tend to attach to swim wear, dive suits and hair, so the skin under covered areas of the body and around the back of the neck are most affected. Friction between the skin and coverings can trigger the nematocysts, as can changes in osmotic pressure caused by the transition from salt to fresh water or the drying out of the nematocyte.

The main symptom of SBE is the appearance of raised and itchy red welts/blotches that appear 4 to 24 hours after diving, although the initial sensations from stings can occur while still in the water. Individuals who have previously suffered from SBE may develop a sensitivity to the proteins in the nematocyst’s venom and therefore react more rapidly upon reexposure. The skin disorder usually resolves within a week, but may return after several weeks or even longer. Depending on exposure and individual sensitivity, there may also be fever, headache, nausea, vomiting, generalized weakness, chills, diarrhea, aching joints, muscle spasms and headache.

How to Prevent Exposure

• Check local health agencies for a status report. Some, like the Cayman Islands Health Services, Accident and Emergency Department, may issue a warning if the local situation gets bad enough. Also ask resorts and dive shops if they are aware of heavy infestation. If the answer is in the affirmative, you can always skip the diving .

• Apply a thin layer of SafeSea (read about it in the October 2000 issue of Undercurrent) . Developed by an Israeli scientist, it is designed to keep nematocysts from being activated, and has both research and anecdotal reports of effectiveness. It is not 100 percent effective, however, so do take all the other preventive steps discussed here as well. You may also apply sun screen, baby oil or petroleum jelly to the skin.

• Wear a snug fitting full body protective suit that fits tightly at the neck, wrist and ankle. Swim suits and T-shirts are not recomm ended .

• When ascending from a dive, p e rform your safety stop at around 20í, below the depth at which most larvae typically hang. When it’s time to surface, vigorously purge your second stage above your head as you ascend and get off the surface as rapidly as possible. If on a night dive, turn your light off at the safety stop and keep it off.

• Remove wet garments immediately and wash yourself thoroughly. Do not rinse off with any items on.

How to Treat Stings

If you do get stung, apply a mixture of isopropyl alcohol and vinegar to the affected areas. If unavailable, use pure vinegar or Windex. Alternatively, apply a thin poultice of meat tenderizer and allow it to dry. In place of these measures, some find it effective to rub the area with papaya. However, whatever you do, do it immediately upon becoming aware you’ve been stung; Bathing in or applying colloidal oatmeal, which can be purchased at the pharmacy or grocery store, may afford additional relief.

Follow these actions with the topical application of hydrocortisone cream/lotion, twice a day. If you do not have or wish to use hydrocortisone, a calamine preparation with menthol can be applied. If your reaction is strong and you are able to take an oral antihistamine, consider doing so. However, be aware that some of these drugs cause drowsiness and may be unsafe for use while diving; and wash all garments well in warm, soapy water and let dry completely before wearing again.

Remember that if you have a severe allergic reaction, don’t get substantial resolution from self treatment, or the eruption seems to be getting worse or infected, you should seek medical attention in a timely manner.

---Doc Vikingo

PS: To order SafeSea call 1/800/826-0440 or go to their Web site at

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