Dehydration and FreeDiving

Definition: dehydration (hypohydration) is defined as the excessive loss of body water, with an accompanying disruption of metabolic processes.

There are two kinds of divers- those who pee in their wetsuit, and those who lie about not peeing in their wetsuit...


  • Water covers over 70% of the planet
  • Our body consists of over 70% water
  • Our muscles and brain consist of over 70% water
  • A loss of 2% of our total water content is considered Dehydration and will have serious effect on performance.
  • Beyond a certain point, dehydration could be fatal.
  • Our body can only operate within a very narrow range of temperature and fluid levels.
  • Water helps lubricate our joints, increases focus, maintains balance in our blood, allows for better O2 transportation, removes toxins and more.

In practical terms for FreeDivers- When a diver spends a prolonged duration in the water they will experience an increased urge to pee. This is caused by the onset of the dive response. When we dive, our body is exposed to pressure and loss of gravity that causes blood to leave the limbs and flow into the core. As a result our body thinks we have too many fluids and causes the kidney to produce more urine. When we leave the water the body "realises" he actually has not enough fluids and limits urine production.

As we tend to perform high intensity activities such as swimming against currents, Diving up and down, climbing on the boat and generally spend hours in a thick, black rubber wetsuit we lose a lot of fluids. A FreeDiver will not feel that he is losing fluids while diving unless the water is warm and he wears a thick wetsuit. Lastly, we expel a high amount of water through the respiratory process.

Symptoms of Dehydration:

  • Increased thirst
  • Dry mouth and swollen tongue
  • Weakness
  • Dizziness
  • Palpitations (feeling that the heart is jumping or pounding)
  • Confusion
  • Sluggishness
  • Fainting
  • Inability to sweat
  • Decreased urine output

The effect on our performance

Loss of fluids to a volume of 1% of our total volume will reduce performance by around 10%! This will mean that a FreeDiver will have a significant decrease in his ability to dive deep or spend more time under the water. Dehydration affects our mental capacity and our ability to assess complicated situations, which in turn might increase the risk of an emergency.

As dehydration makes our blood more thick it causes the heart to work harder which consumes more O2. As a result – a big drop in our ability to hold our breath.

Dehydration will also increase the risk of DCS (Decompression sickness). DCS has become an issue in recent years as FreeDivers / Spearfishermen began diving to great depths or have performed repetitive dives with short recoveries.

Many Freedivers (and scuba divers) notice that their equalization becomes harder as the day progresses. This is partially as a result of dehydration.

Not enough water in our muscles will increase the likelihood of cramps.

A dehydrated FreeDiver has an increased risk of a shallow water blackout.


Most FreeDivers take water on the boat when they go out diving. Water might sound like the logical choice for hydration as this is what the body loses. An average male should consume around 3L of water per day (a woman should consume around 2L). Unfortunately, water lacks all the essential minerals our body loses when we sweat and pee. Although drinking water is good, it will actually end up producing the opposite effect of what we want. In order to hydrate the proper way we need to consume fluids that contain minerals. A good example would be an isotonic drink.

In practical terms:

  • Drink water regularly and not in one go – a cup of water per 15 minutes is better than 500ml every hour as it allows better absorption.
  • Drink even if you feel you do not need to drink – In the water, our body "thinks" it is over-hydrated, making us feel we do not need to drink.
  • Choose your wetsuit according to the water temp – a 5mm wetsuit in 23 degree water will cause overheating and dehydration.
  • Stay out of the sun when on the boat to minimize exposure and fluid loss.
  • Drink fluids that contain salts and sugars (Avoid energy drinks such as redbull as they contain caffeine).

The bottom line:

As FreeDiving is a physical activity that is performed in a high resistance medium we must make sure our body and mind are both in their optimal state. Proper hydration will ensure the body is balanced and that the muscles could operate at their peak. Once our mind is nourished – it will allow us to think fast, react fast and be able to solve any emergency that presents itself.