Caffeine has a mild diuretic effect, but at normal intakes the water in your cup far outweighs what you lose. One study even found that four cups of coffee a day hydrate about as well as the same amount of water. The NHS counts tea and coffee towards your fluid intake. The only limit is the caffeine itself.
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.