Diver Dehydration

Dehydration has several profound physiological effects relevant to diving. Firstly, it leads to a reduction in blood volume, causing the blood to become thicker (increased viscosity). This makes it harder for the heart to pump blood efficiently and reduces the body's ability to transport oxygen and nutrients, as well as remove waste products.

Crucially for divers, a reduced blood volume and increased blood viscosity can impede the off-gassing of inert gases, such as nitrogen, from tissues during ascent. This means nitrogen bubbles, which cause decompression sickness (DCS), are less efficiently removed from the body, significantly increasing the risk of a bend. Furthermore, dehydration can lead to fatigue, muscle cramps, and impaired cognitive function, all of which can compromise safety and decision-making underwater.

Several factors contribute to dehydration during diving activities. Breathing dry, compressed air from a cylinder is a significant culprit; this air is dehumidified, and as it warms in your lungs, it absorbs moisture from your respiratory tract, which is then exhaled, leading to considerable fluid loss with every breath.

Immersion diuresis is another key factor: the body's physiological response to being submerged in water. The pressure and temperature changes cause blood to be shunted from the extremities to the core, which the kidneys misinterpret as an increase in fluid volume, prompting increased urine production. Additionally, the exertion of diving, sweating in warm climates, sun exposure, seasickness, and even consuming diuretics like caffeine or alcohol, all exacerbate fluid loss, making a conscious effort to rehydrate vital.

Liveaboard diving presents unique challenges for maintaining hydration. With multiple dives often scheduled daily in tropical environments, the cumulative effect of fluid loss can be substantial. It's imperative to adopt a proactive hydration strategy from the moment you board.

Start your day with a large glass of water, and aim to drink small, frequent amounts of water or electrolyte-rich fluids throughout the day, especially between dives. Avoid excessive consumption of coffee, tea, and alcohol, as these can act as diuretics. Many liveaboards offer ample drinking water, but consider bringing a reusable water bottle to ensure constant access. Pay attention to the colour of your urine – a light straw colour indicates good hydration, while dark yellow suggests you need to drink more. Prioritising hydration will not only enhance your safety by reducing DCS risk but also improve your overall energy levels and enjoyment of your liveaboard adventure.

Myth: Drinking lots of water just before a dive is enough. Fact: Hydration is an ongoing process. 'Pre-loading' with water right before a dive won't compensate for chronic dehydration and can lead to discomfort. Consistent fluid intake throughout the day, especially between dives, is far more effective for maintaining optimal hydration.

Myth: As long as I'm not thirsty, I'm hydrated. Fact: Thirst is often a sign that you are already mildly dehydrated. By the time you feel thirsty, your body's fluid balance is already compromised. Proactive and consistent fluid intake is key, rather than waiting for thirst to signal a need to drink.

Myth: Soft drinks or alcohol count towards hydration. Fact: Sugary soft drinks can contribute to dehydration due to their high solute concentration, and alcohol is a known diuretic, meaning it increases urine production and fluid loss. While some juices or sports drinks can help with electrolytes, plain water remains the best choice for hydration.