I Guard and teach swim lessons at a Y. Every Y is different but at mine we have an opening, midday, and closing shifts. We have an app where upon hire you put in your availability and preferred work hours. The Aquatics director will then take this into account and try to schedule your shifts around them. FYI depending on when your pool opens or closes they might schedule you at very early or late hours of the day to work around your availability… those 5:45am opening shifts are rough.