Nola and I on our dinghy and Ed and Joy on their dinghy all went snorkelling the same reefs at the same time. I got Sea Lice, but Joy got it worse, my wife Nola had none , neither did Joy's husband Ed ! While my experience was more of an inconvenience, Joy was physically Ill. Different people can have different reactions to similar exposure levels. Once having had a reaction to it, it seemed as though I became supersensitive to such irritations in the spring time for the next couple of years. A passenger would drop a mask while climbing up the ladder. It would only be in 12-15 feet of water so I would put my mask on hold my breath as I jumped in, swim down retrieve the lost mask, climb the ladder, probably in the water less than 45 seconds yet I would get eruptions from that short an exposure ! They say if you dive naked the larval anemones or lice won't get you, but I am more the advocate of wearing a tee shirt regardless to PROTECT YOUR NECK AND DOWN YOUR SPINE.

If you are unfortunate enough to get stung by a mature Portuguese Man-O-War ( the man-o-wars medusa or stinging cells can extend over 40' from the hydrozoa or floating sac), around your neck, down your spine you could suffer from respiratory paralysis and drown from being unable to breath. Man-o-war stings are VERY Painful and can induce shock into a victim. We Used to consider Man-o-wars a seasonal threat, from November thru April. The only natural predator of the Portuguese man-o-war are our sea turtles. Sea turtles nesting season starts in April and it was thought that as the sea turtles congregated closer to shore as they gobbled up the M.O.W the man-o-war would disappear for the summer (predated out). Now with fewer and fewer sea turtles to gobble them up, the man-o-war are a MUCH greater threat than they used to be and it is now no surprise to see a M.O.W. out in July or even August, instead of their normal blue color, they turn pink in the summertime almost like they are getting sunburned and each year they are considered more of a year round threat and less of a seasonal one. In the winter time snorkelers are more likely to be wearing a wetsuit or other covering because the water is colder. I have had many many snorkelers stung by manowar's medusa, even when there were NONE IN SIGHT! the medusa are not strong and break easily and can just float (nearly invisible!) waiting for something to sting. I have seen Man-a-war KILL small fish, fish protected by a layer of slime and scales, human skin is no match for the power of a manowar's sting, they will HURT YOU, protect your self, get a dive skin, tee-shirt what ever but at the very least cover your neck and your back down your spine. I hope everyone tries to take the time to retrieve plastic bags floating at or near the surface. Sea turtles do not have good eyesight and are said to often mistake a floating plastic bag for one of their favorite foods the Man-o-war. The plastic can can suffocate them or if they swallow the plastic it can lodge in their guts, disrupt heir feeding and cause them to slowly starve to death.

Less Sea Turtles = more man-o-war.

Please retrieve plastic whenever possible and help our friends the sea-turtles.

Not to blow the dangers out of proportion, while the threat Jellyfish pose are a concern, a greater threat to novice snorkelers and scuba divers is Exhaustion.

I have seen people panic because they started to get tired and didn't think they could make it back to the boat. Several Snorkelers DIE in the Keys EACH YEAR from what I suspect are stress induced heart attacks. Wear some flotation like a ski belt, learn to just relax and rest WHILE you are IN the water.

Do NOT WEAR Jewelry snorkelling!

People getting attacked by say a barracuda for a flashy piece of jewelry is a very rare occurrence but can happen and is more likely to happen in murky water than in clear water. I don't know the proportion of married people I took snorkelling but I would guess about one in a thousand lost a wedding ring (more men than women). One poor guy had been married on Friday and came to the Keys for his honeymoon and lost his ring Sunday Morning.

I just had a Capt tell me the other day one of his passengers lost (What was claimed to be) an $8 thousand dollar earring, what an idiot to bring such a valuable piece into the water snorkelling! Make sure your watch is waterproof, your pockets are empty, do not interact with any of the marine life, do not try to pet anything, do not try to pull anything by the tail, do not try to take anything for ride. Do not splash and thrash while snorkelling, try to go slowly, do not touch living coral or allow your equipment to touch living coral, do not panic, STAY WITH YOUR BUDDY, CONSERVE YOUR ENERGY, wear at least a t-shirt for protection.