Swimming pools need to maintain a delicate balance of dissolved chemicals to remain clean and safe to swim in. Often swimming pools can become too acidic due to too much acid being used to kill bacteria. In these cases, baking soda can be added to counteract this.
A pool which has too much acid in it is a pool with a low pH. This acidity in a swimming pool can irritate both the eyes and the skin. In order to remedy this, baking soda can be added. This works to increase the pH of the pool as it functions as a pH buffer, moderating some of the pool's acidity, and hence making it more comfortable to swim in.