Everyone is aware of how important hydration is in at least some capacity. Whether you learned that the majority of the human body is made up of water, or that you can potentially survive weeks without food, but going even just a few days without water can be extremely dangerous. There remains no doubt that we all need water to function. This is especially true for athletes, where being properly hydrated or not can have such drastic effects on performance. Ironically, swimmers commonly become dehydrated as well. Perhaps being in water for the majority of our training makes us forget that we are still sweating and expending fluid just as much as we would doing anything else.
Simply put, dehydration is the point at which you are taking in less fluid than you are expending through your bodily processes, leading to a decrease in the overall amount of water in your body.
Since more than half of your body weight should consist of water at any given time, disrupting this equilibrium can have many negative effects. For instance, your blood is roughly 90% water, meaning that a dehydrated person actually has less blood volume than they should. Blood is responsible for making sure the various systems of the body continue to function, carrying oxygen, electrolytes, and nutrients to muscles and organs. These are essential to not just athletic performance, but the overall function of your body. Because of this, dehydration can cause an increased risk of injury, slower reaction times, less endurance, and even cramps, which can occur as a direct result of your muscles not receiving enough blood flow due to your body prioritizing essential organs.
Fortunately, all of this is easily avoidable by simply drinking water or other fluids throughout the day. It is increasingly common to hear that you should drink eight glasses of water a day, which is good as a general rule. However, not everyone is the same size, and the exact amount of fluid each person needs varies between individuals. Which means you should also be sure to avoid drinking too much water, which can be as bad as not having enough.