When You are operating a PWC in an area where swimmers are in the water. When must you slow your PWC to idle speed?

When operating a personal watercraft (PWC) in an area where swimmers are present, you must reduce your speed to idle speed when you are within 100 feet of the swimmers. This is to ensure the safety of individuals in the water and to minimize the risk of collisions. Additionally, always be vigilant and aware of your surroundings to avoid any potential hazards.