Which of the following is a symptom of improperly balanced pool water?

Skin irritation and rashes are indeed symptoms of improperly balanced pool water. When pool water chemistry is not properly balanced, particularly the levels of pH, total alkalinity, and chlorine, it can lead to various discomforts for swimmers. A high or low pH level can irritate the skin and cause rashes, while imbalanced chlorine levels can lead to chlorine burns or irritation as well. Maintaining proper water chemistry is essential not only for user comfort but also for protecting the pool's infrastructure and equipment.

The other options present characteristics that are either neutral or positive and do not indicate issues with water balance. Prominent water clarity suggests that the pool’s filtration system is working well, which is typically a sign of balanced water. Increased user satisfaction and desirable water temperature also point toward a well-maintained pool environment without the adverse effects associated with improper water balancing.