Crazy test

One day a doctor of the insane asylum was examining the progress of the three insane people. If you pass the test, you will be released, and if you do not, you will be detained for two more years. The doctor told the three of them to jump in front of a waterless swimming pool. The first madman immediately jumped up and broke his leg. The second lunatic also jumped like a doctor and broke his arm. But the third madman did not agree to jump at all. The doctor shouted for joy and said, "Hey, you're all right."But the third madman did not agree to jump at all. The doctor shouted for joy and said, "Hey, you're all right." I will set you free today. Well tell me why you did not jump? He replied, ‘I know how to swim