Why Do I Feel Sick After a Dive? Understanding and Preventing Post-Dive Nausea

Diving into the underwater world is an exhilarating experience, but for some, the joy of a dive can be followed by an unwelcome bout of nausea or even vomiting. If you've found yourself feeling sick after a dive, you're not alone. This common post-dive complaint can stem from a variety of factors, some easily preventable, others requiring a bit more attention to your diving practices and physiology. Let's dive into the common culprits behind that queasy feeling.

1. Motion Sickness (Seasickness)

This is perhaps the most frequent reason divers feel unwell after spending time in the water. Our inner ear, responsible for balance, receives conflicting signals when you're diving. While your eyes might be telling your brain you're stationary, the motion of the water, waves, and currents sends different messages to your vestibular system. This sensory conflict can lead to symptoms of motion sickness, including nausea, dizziness, and vomiting. The rocking motion of the boat to and from the dive site can also contribute significantly.

Preventing Motion Sickness:

Medication: Over-the-counter or prescription motion sickness medications can be highly effective. Take them as directed, usually before you feel sick.
Stay Hydrated: Dehydration can worsen motion sickness. Drink plenty of water before and after your dive.
Avoid Alcohol and Fatty Foods: These can irritate your stomach and exacerbate nausea. Opt for bland, easily digestible meals before diving.
Focus on the Horizon: On the boat, try to fix your gaze on a stable point on the horizon.
Fresh Air: Getting fresh air can often alleviate symptoms.
Acupressure Bands: Some divers find relief using acupressure wristbands.

2. Decompression Sickness (DCS) - The "Bends"

While less common than motion sickness, feeling sick after a dive can also be a symptom of Decompression Sickness (DCS), often referred to as "the bends." This occurs when dissolved nitrogen in your body's tissues forms bubbles during ascent if you ascend too quickly or exceed your no-decompression limits. Nausea can be one of the early, mild symptoms of DCS. Other symptoms can include joint pain, dizziness, fatigue, and skin rashes. If you suspect DCS, seek immediate medical attention.

Key Considerations for DCS Prevention:

Follow Dive Tables/Computers: Adhere strictly to your dive tables or dive computer's guidelines for depth and time.
Slow Ascents: Ascend slowly, ideally at a rate of 30 feet per minute (or slower), with safety stops as recommended.
Avoid Flying or High Altitudes After Diving: Allow adequate surface intervals before flying or going to high altitudes.
Stay Hydrated: Good hydration helps your body off-gas nitrogen more efficiently.
Avoid Strenuous Activity After Diving: Conserve energy and allow your body to recover.

3. Carbon Dioxide Buildup

This can happen if you're breathing too shallowly or too rapidly, or if your dive gear is not functioning optimally. When carbon dioxide builds up in your bloodstream, it can lead to symptoms like headaches, dizziness, shortness of breath, and nausea. Overexertion during the dive can also contribute to CO2 buildup.

Preventing CO2 Buildup:

Proper Breathing Technique: Focus on slow, deep breaths throughout your dive.
Avoid Overexertion: Pace yourself and conserve your energy.
Equipment Checks: Ensure your regulator is functioning correctly and your breathing rate is comfortable.
Fitness for Diving: Being in good physical condition can help you manage your breathing more effectively.

4. Dehydration

It might surprise you, but divers often become dehydrated. The dry air in your tank, the effort of breathing underwater, and the salt water exposure can all contribute to fluid loss. Dehydration can lead to a variety of symptoms, including nausea, headaches, and fatigue. It also increases your risk of DCS.

Staying Hydrated:

Drink Water Regularly: Sip water throughout the day before, during surface intervals, and after your dives.
Avoid Diuretics: Limit your intake of caffeine and alcohol, as they can dehydrate you.
Electrolyte Drinks: For longer trips or very active dives, consider electrolyte replacement drinks.

5. Ear Barotrauma and Inner Ear Issues

Problems with your ears can also cause nausea. If you experience difficulty equalizing pressure during descent or ascent, you could develop ear barotrauma. This can lead to pain, dizziness, and nausea. Issues with your inner ear, which is responsible for balance, can also be triggered or exacerbated by diving, leading to vertigo and sickness.

Addressing Ear Issues:

Proper Equalization Techniques: Learn and practice effective equalization methods (e.g., Valsalva maneuver, Frenzel maneuver).
Never Force Equalization: If you can't equalize, ascend slightly and try again. Don't force it.
Avoid Diving with Congestion: Never dive with a cold or sinus congestion, as this significantly increases your risk of ear barotrauma.
Consult a Doctor: If you experience persistent ear pain, dizziness, or hearing loss, seek medical advice.

6. Food Poisoning or Upset Stomach

Sometimes, the cause of your sickness is not directly related to the dive itself. You might have eaten something that disagreed with you before or after the dive, or you could have a stomach bug. While it's tempting to blame the dive, consider other possibilities.

What to Do:

Assess Your Diet: Think about what you ate in the hours leading up to and after the dive.
Hydrate: Sip on clear fluids like water or clear broths.
Rest: Allow your body to recover.
Seek Medical Advice: If symptoms are severe or persistent, consult a healthcare professional.

7. Nitrox Diving Considerations

If you're diving with enriched air nitrox, it's crucial to know your gas mix and adhere to the shallower depth limits associated with it. Exceeding these limits can lead to oxygen toxicity, which can manifest with symptoms like nausea, visual disturbances, and even convulsions. Always confirm your nitrox mix and ensure your dive computer is set correctly for it.

Nitrox Safety:

Accurate Analysis: Always analyze your nitrox tank before each dive to confirm its oxygen percentage.
Respect Depth Limits: Never exceed the maximum operating depth (MOD) for your specific nitrox mix.
Dive Computer Settings: Ensure your dive computer is programmed for nitrox and is set to the correct FO2 (fraction of inspired oxygen).

When to Seek Medical Attention

While mild nausea can often be managed with home remedies and preventative measures, it's important to know when to seek professional help. If your nausea is severe, persistent, or accompanied by any of the following symptoms, you should consult a medical professional immediately:

Severe headache
Dizziness or vertigo
Numbness or tingling
Weakness or paralysis
Difficulty breathing
Unusual fatigue
Joint pain
Confusion or disorientation

These could be indicators of more serious conditions like Decompression Sickness or other medical issues. Always err on the side of caution when it comes to your health and well-being.

Frequently Asked Questions (FAQ)

Why do I feel dizzy after a dive?

Dizziness after a dive can be caused by several factors. Motion sickness, due to conflicting sensory input to your inner ear, is a common culprit. Decompression Sickness (DCS) can also cause dizziness as an early symptom. Additionally, inner ear issues, CO2 buildup, or even dehydration can contribute to feelings of dizziness.

How can I prevent feeling sick on a dive boat?

To prevent sickness on a dive boat, which is often a precursor to feeling sick after a dive, focus on managing motion sickness. Stay hydrated, avoid heavy or greasy meals and alcohol, and get plenty of fresh air. Looking at the horizon can also help. Over-the-counter motion sickness medication taken before boarding is also a very effective strategy for many.

Is nausea a sign of Decompression Sickness?

Yes, nausea can be one of the early, mild symptoms of Decompression Sickness (DCS). While not every instance of nausea after a dive is DCS, it's crucial to be aware of other potential DCS symptoms and seek medical attention if you suspect it, especially if the nausea is accompanied by joint pain, numbness, or weakness.

What should I eat before a dive to avoid feeling sick?

Before a dive, it's best to eat a light, easily digestible meal. Opt for foods like toast, crackers, fruit, or a simple carbohydrate-rich meal. Avoid greasy, spicy, or heavy foods, as well as excessive alcohol or caffeine, which can irritate your stomach and contribute to nausea or dehydration.