A sudden onset of illness or a sharp headache while scuba diving is an immediate emergency that demands action. Ignoring symptoms, even minor ones, can quickly escalate the situation due to the underwater environment and pressure changes. Any diver experiencing an unexpected physical complaint must recognize that continuing the dive requires an immediate, controlled termination. This urgency stems from the potential for rapid progression of injuries like decompression sickness or lung overexpansion, which can lead to severe neurological injury or death.
Immediate Underwater Response
The first reaction to feeling ill must be to stop all activity and signal your buddy immediately using the universal distress sign (a hand wobbling back and forth). Once acknowledged, use the thumbs-up sign, which means to ascend and end the dive. This communication is non-negotiable, and the dive must be aborted regardless of the remaining time or planned depth.
The priority shifts to managing the ascent with control, swimming upwards at a rate not exceeding 30 feet (9 meters) per minute to minimize the risk of gas-related injuries. Maintaining neutral buoyancy is paramount, so the diver must use their buoyancy control device (BCD) in small, controlled bursts. A continuous, gentle exhalation is required throughout the entire ascent to prevent lung overexpansion injury as the air in the lungs expands with decreasing pressure.
If air supply allows, the buddy pair should conduct a safety stop at 15 feet (5 meters) for three minutes, as this pause aids in nitrogen off-gassing and is part of a conservative ascent profile. However, if the diver’s symptoms are rapidly worsening, the controlled ascent to the surface takes precedence over a safety stop. Managing stress by focusing on slow, deep breaths is the only way to avoid panic, which is the leading cause of diving accidents.
Identifying Potential Causes and Associated Symptoms
The sudden feeling of illness underwater can be a symptom of several serious physiological conditions specific to diving. A pounding, throbbing headache, sometimes accompanied by labored breathing, points toward carbon dioxide ($CO_2$) retention or toxicity. This occurs when a diver hypoventilates, allowing the metabolic waste gas $CO_2$ to accumulate, which acts to dilate cerebral blood vessels.
Localized, sharp pain in the forehead, cheeks, or around the eyes, often worsening on descent, is typically a sign of sinus barotrauma, or a “sinus squeeze.” This painful condition results from a pressure differential between the sinus cavities and the ambient water pressure, usually due to congestion preventing proper equalization. Conversely, the headache associated with decompression sickness (DCS) is often more severe, accompanied by profound fatigue, nausea, or joint pain, and may only manifest after surfacing.
Dehydration is a significant factor, as it thickens the blood, reducing plasma volume and impairing the body’s ability to off-gas inert nitrogen, thus increasing the risk of DCS. General malaise, dizziness, or a non-specific headache can stem from simple dehydration or overexertion. Because the symptoms of mild DCS can mimic those of less severe conditions, every post-dive headache or feeling of illness must be treated with suspicion.
Surface Protocol and Medical Assessment
Once the diver is safely on the surface, the focus immediately shifts to medical management. The first action is to administer 100% oxygen using a demand valve or non-rebreather mask, if available. Breathing the highest concentration of oxygen accelerates the elimination of inert gas bubbles from the bloodstream and tissues, which is the preferred immediate first aid for any suspected decompression illness.
The injured person should be kept warm, treated for shock, and placed in a position of comfort. The most important step for professional medical intervention is to contact a dive emergency hotline, such as the Divers Alert Network (DAN), to consult with a diving medicine specialist. These experts can provide guidance on first aid and coordinate evacuation to a hyperbaric chamber if necessary.
Accurate documentation is required for the medical team and is often overlooked in the stress of the moment. The dive profile, including maximum depth, bottom time, ascent rate, and any completed safety stops, must be recorded precisely. Additionally, a detailed list of the symptoms, the time of their onset, and the first aid administered must be prepared for emergency medical services (EMS) personnel.