Legionella bacteria, which cause Legionnaires' disease, a sometimes severe pneumonia, thrive in stagnant water between roughly 25 and 45 °C (77 to 113 °F). Above 60 °C (140 °F), they are quickly killed. People get infected by inhaling fine water droplets, in the shower for instance. Hence the advice not to set a hot-water tank too low, around 55 to 60 °C, and to run the taps for a while after a long absence.
Chlorine on its own is fairly gentle. But when it combines with urine, sweat and other grime from swimmers, it forms chloramines, which cause stinging eyes and that classic 'chlorine smell'. A well-kept pool barely smells at all. Shower before you swim and never pee in the water.
Muscle mass slowly shrinks with age, putting independence at risk. But in 1990, a study had nursing home residents aged 86 to 96 train their legs for eight weeks: their strength more than doubled. Muscle responds to training at any age. Getting up from a chair without using your hands is already an exercise.