I applied to be a life guard awhile ago. You must be a part of a safety force, have the ability to swim/breath under water, and there is also a course you have to go through. In the class you will learn first-aid techniques like CPR. You'll also learn stuff like how to treat cuts, wounds, burns, ect. Also they will teach you about safety, equipment usage, and how to use tools around the pool or beach. I read something about my community pool hiring, so i gave them my information, they interviewed me after i took the class, got the job, and never had to do anything out of the ordinary. Thankfully everyone was safe when i was watching them, but besides constantly having to tell people to stop running, its a pretty cool job. Just ask pools or beaches around your area if they would be interesting in hiring you after you made all the necessary protocalls
The application process varies from pool to pool the best thing to do is call them and ask them that exact same question.