Stamina is the ability to sustain physical or mental effort over a period of time without becoming exhausted. Swimming is a physical AND mental game!! What are some exercises or tricks you can do to build it? 1. Do not breathe until 3 strokes AFTER you flip turn before bilateral breathing. This helps train your lungs to endure more and will soon become a habit 2. Utilize kick boards AND pull buoys to enhance muscle strength so when you actually do the stroke, it will feel much lighter 3. Do multiple drills and continue to elongate the duration of them 4. Push yourself harder by not taking as many breaks (mental strength!!) Your body and mind can endure more than you think!!!