I understand. The size of the pool tho isn’t the consideration. You just have to keep moving, even if that means more turns. The cooler water is good as water cooler than body temperature 97 to 99 degrees Fahrenheit burns more calories as it deflects heat away from exercising muscles.
Find some exercise program that you like and will do 5 times per week for 30 minutes to maintain your weight. Exercise is most effective at changing the composition of your body i.e. less fat, more muscle. Muscle burns calories. Body fat just sits there storing fuel while waiting for a famine which never comes. Fat can be mobilized out of storage with aerobic exercise like swimming which needs food carbohydrates and oxygen to burn completely.