Too high a pH will interfere with the action of the chlorine, too low a pH will cause eye and skin irritation. Too much stabilizer will interfere with the chlorine. Small children are fascinated with the shiny surface and blue depths of a pool. They don't recognize the danger there, and in experimenting with this fascinating phenomenon may fall in and drown. Building codes mandate enclosure of all pools with building walls or durable fence at least 4 feet high.
Diving is probably the most dangerous thing one can do in a pool.
Injuries to the neck and spinal column in diving mishaps often cause paralysis and death. Never dive in a pool if your trajectory will place you in an area less than 8 feet deep. If you are diving from a board, deeper water may be necessary. Keep a long pole or shepherd's hook ready on the pool deck to help pull someone in distress to the safety of the pool side. Learn CPR and other basic lifesaving techniques.