Private ScubaDiving InformationHealth and Safety › Immersion Diuresis

Immersion Diuresis: Why Does it Happen

The increased need for scuba divers to urinate when the body is immersed in water, especially cold water, is easily explained.

This article explains why immersion diuresis happens (the urge to urinate in water) and how divers can reduce the likelihood of having to pee during a dive.

Why Scuba Diving Makes You Want to Pee

In a nutshell, scuba diving gives people the opportunity to explore the underwater world.

Yet, almost all divers will experience a strange phenomenon known as "immersion diuresis".

Does it fall under the scuba diving health restrictions? No... not at all.

Even so, the increased and persistent urge to urinate while submerged is a cause of concern for many - especially beginners.

Despite being a completely natural and well-documented physiological response, it can be inconvenient or a little embarrassing. But, you can enhance your diving experience if you understand why immersion diuresis happens and how best to manage it.

Why Does the Urge to Urinate Occur Underwater?

Immersion Diuresis

The primary reason why scuba divers feel the urge to urinate is a process called immersion diuresis. When you are submerged in water, especially when scuba diving in icy cold water, the human body will experience an increase in hydrostatic pressure.

As a consequence of that, the blood vessels in the extremities get narrower (a process called vasoconstriction) and shift blood toward the core organs, especially the heart and lungs. It also increases the blood volume in the central circulatory system.

In response, the kidneys start working harder to reduce this perceived overload of fluid. The result is more urine - which in turn leads to a greater frequency of urination.

Put another way:

Antidiuretic hormone (ADH) is the hormone that controls the production of urine (e.g. by the kidneys). It controls how much urine the kidneys produce (and the frequency of production).

The fluid overload causes a cessation in ADH production. In turn, the kidneys immediately produce more urine to try and lower the centrally circulating blood volume. So, it is an automatic response by the body to preserve blood volume.

Thermoregulation in Scuba Diving

Our free online scuba training section explains how water absorbs heat from the body about twenty five (25) times faster than air. As a result, temperature regulation can sometimes be a significant challenge for divers.

Yet, even when you wear a neoprene wetsuit or drysuit, prolonged exposure to cool water can lead to the onset of mild hypothermia symptoms (e.g. heat loss management).

The body's reaction is to try and conserve heat by constricting the blood vessels. But, this process can also trigger immersion diuresis.

Best Hydration Practices

Proper hydration is essential for scuba divers to avoid dehydration caused by breathing compressed air, excessive exertion underwater, and exposure to saltwater.

Thus, drinking water before a dive can also compound the effects of immersion diuresis and amplify the urge to urinate while scuba diving.

How Can Divers Avoid Immersion Diuresis?

Even though avoiding immersion diuresis entirely is difficult, there are several strategies that you can try to reduce its effects. Here are some scuba diving tips to help new divers manage the increased urge to pee underwater:

Pro Tip: Even though these strategies can help minimise immersion diuresis, some level of fluid loss is going to be inevitable. But, you can prepare for it by staying hydrated and focusing on making a safe dive. Besides, the blood volume will return to near normal after exiting the water and you will most likely have a full bladder.

Divers also enjoyed reading about...