Know the Risks

Wearing appropriate exposure protection and being aware of the marine life where you are diving will help you reduce the risk of injury from underwater hazards.

Nitrogen narcosis, Irukandji syndrome and inadequate exposure protection

Divers frequently experience jellyfish envenomation, the severity of which can range from mild localized pain to severe systemic symptoms and even death. Envenomation by certain box jellyfish can cause a rare condition known as Irukandji syndrome. An interesting case resulted when a diver experienced Irukandji syndrome in conjunction with nitrogen narcosis, a common phenomenon that is well described in scientific journals and well known to divers.

A 28-year-old diver planned a shore dive with a group off the coast of Piti, Guam, as part of a deep-diving course. The diver had worked an overnight shift and slept for only six hours but was healthy and felt alert. They began with a 200-yard surface swim before descending to 80 feet. From there, the instructor planned to lead the divers another 50 yards along the downward sloping floor to 115 feet for a cognitive function test. After five minutes at depth, the divers would swim back to the first location, repeat the test at 80 feet and then begin a slow ascent to the surface with a five-minute safety stop at 15 feet.

The dive began according to plan, but during the transit to 115 feet the diver noticed his peripheral vision narrowing along with impaired cognitive ability, an intoxicated sensation and a loud pounding in his ears. Although this was the first time he had experienced such symptoms, he attributed them to nitrogen narcosis but decided that he was safe to continue the dive while sticking close to his buddy.

When he arrived at the test site at 115 feet, the diver felt an intense, painful burning sensation along the inside and back of his right thigh that would not go away. With the increasing symptoms of nitrogen narcosis, the diver thought the burning sensation was in his head and ignored it. Although he was wearing only a rash guard and board shorts under his buoyancy compensator, the diver did not suspect a marine life injury. After ascending to 80 feet, the narcosis symptoms spontaneously resolved, but the burning sensation along his thigh continued. The diver noted no other symptoms.

Upon exiting the water after the safety stop, the diver noted that the burning sensation was not resolving. Ten minutes later he experienced unusual fatigue along with abdominal and back cramping, and the burning sensation spread to his torso. Twenty minutes after exiting the water, the diver began coughing up white, frothy sputum. His muscles felt too weak for him to stand upright, and he needed to bend over and rest his forearms on his legs. The diver alerted his dive instructor, who advised him not to go on a second dive and to seek medical attention.

The diver called a friend who is a physician with dive medicine training. Due to the dive profile and the symptoms, the physician also suggested that the diver visit a local hospital for an evaluation. But because of a lack of financial resources, the diver decided to avoid the hospital and rest at home.

The diver experienced increasing pain for the next four hours due to abdominal and back muscle cramping and the continued burning sensation on his right thigh and torso. The productive cough with sputum also continued. He tried to sleep it off but was unable to fall asleep due to pain and restlessness. The symptoms gradually resolved over the next five hours. His symptoms were mostly gone by that evening, and he was able to fall asleep.

The diver’s cough had entirely resolved by morning, and the tingling sensation dissipated over the next three days.

Nitrogen Narcosis

Nitrogen narcosis symptoms include an intoxicated feeling, impaired judgment, difficulty concentrating and drowsiness along with moods ranging from overconfidence and euphoria to fear and insecurity. At extreme depths of more than 400 feet, divers can lose consciousness. Nitrogen narcosis symptoms can make diving dangerous, because divers may make poor decisions.

Fatigue, depth, personal history of susceptibility, alcohol intoxication before a dive and cold water are factors that may increase the likelihood of nitrogen narcosis, which typically resolves spontaneously when the diver ascends above the depth where the symptoms initially appeared. In the case described in this article, the diver’s fatigue, description of symptoms and resolution with ascent suggest that he might have been experiencing nitrogen narcosis.

The diver should have immediately ended the dive upon developing symptoms. Poor decision-making, a false sense of security or overconfidence combined with ignoring the possibility of a hazardous marine life injury could lead to a bad outcome, which, fortunately for this diver, did not happen.

Irukandji Syndrome

Certain species of box jellyfish cause Irukandji syndrome. The symptoms, which manifest throughout the body, most commonly include abdominal pain, backache, nausea, restlessness and hypertension that develop five to 90 minutes after the sting. More than nine jellyfish species in Australia are formally identified as causing Irukandji syndrome, but reports in places such as the United Kingdom, Hawaii, Thailand and Florida indicate that other species of jellyfish not yet formally identified may also induce the condition.

Most Irukandji syndrome cases resolve spontaneously in hours to days, but 3 percent of reported cases progressed to heart failure. Other life-threatening complications include acute pulmonary edema and stroke. Although this syndrome can have severe consequences, it is relatively rare.

Although the diver in this case did not see a jellyfish sting him, his symptoms strongly suggest Irukandji syndrome. The cough and sputum likely indicate some level of pulmonary edema. The dive occurred in an area known for box jellyfish and reports of Irukandji syndrome cases. Fortunately, the diver’s symptoms resolved without treatment. The diver acknowledged months later that he did not understand the potential seriousness of his condition at the time. If he had, he would have gone to the emergency department.


Nitrogen narcosis can lead to deadly consequences. Understanding the risk factors and ensuring that you and your dive buddies have discussed how to mitigate risk can potentially save lives.

If you are stung by a jellyfish, watch for symptoms associated with Irukandji syndrome. If symptoms develop, know that it is a potentially deadly condition that doctors can help treat. Pay attention to local marine life bulletins and announcements. The best ways to mitigate jellyfish envenomation risk are to wear full exposure suits and avoid jellyfish when they are prevalent in the water.

Clothing such as loose rash guards, board shorts and T-shirts won’t protect you from free-floating stingers and in some cases may trap stinging planktonic life against your skin. Full wetsuits provide more than thermal comfort; they are also effective barriers against marine life.

© Alert Diver — Q2 2021