The original question was; ‘Why do we pee more often when it’s cold’
We all know the condition that our veins tend to thicken when we are warm. Quit a natural response to the body to call down. The opposite happens when we get cold. The veins tighten, especially the capillary. They just hide a little deeper in the body. Due to the fact the veins tighten the blood pressure goes up. Nothing something to worry about, but your body will respond to this rise. It will start to produce more urine so you will need to pass water!
The kidneys have, besides cleansing the blood from waste, another task. They help in controlling the blood pressure. They do this by giving back more or less water to the blood while filtering it. If your blood pressure is too high, the kidneys will produce more urine and therefore give less water back to the bloodstream. As a result your blood pressure will drop. Due to that you will need to go to the toilet more often. The color of your urine will be more light. If your blood pressure drops your kidneys will return more water (if you have enough) to the bloodstream. The blood volume will increase and as a consequence the blood pressure will rise. You produce less urine.
This process produces about 150 litres of so called pre urine per 24 hours. A hormone called ADH (Anti Diuretic Hormone) makes sure that most of this water returns into the bloodstream. Otherwise you would practically live on the toilet.
Back to those scuba divers. In fact they have to face this phenomena in twofold. The water, also tropical water, will cool down the body fast. The blood vessels will narrow and the blood pressure will rise. On the same hand the overall pressure on the body will increase the more you decent. This pressure make the blood pressure rise as well. The kidneys will respond accordingly and will try to loose some water. So you wet your suit. This is also the reason why it is so important to drink before and after the dive. To avoid dehydration.
For this I bought my own wetsuit. Peeing in your own suit is so much more satisfactory