Water temperature can have a significant effect on the aquatic workout and the overall safety of the participant. Not to mention the comfort of pool users. Extreme cold or too warm water temperature for exercising is generally unsafe. Always make sure that pool temperature is ideal for the age group as well for the activity.
Ideal Water Temperature
For seniors, exercising in cold water is not advised. That is to say anything below 27º. The ideal temperature for this age group is between 27ºC and 30ºC (80ºF - 86ºF)
As for the type of workout, Aqua Aerobics require cooler water temperature than Aqua Pilates for example. When performing an intensive aerobic workout, the maximum temperature should not exceed 27º (77ºF) in order to prevent overheating. In a less intensive workouts like Aqua Pilates, the water temperature should not be less than 28º (82ºF) in order to prevent sudden loss of body's temperature.
Anything less than 25ºC (77ºF) and more than 31ºC (88ºF) could be unsafe.
There is a link between water temperature and burning calories;