What is the least appropriate action to take when a swimmer goes into shock?

Having the person sit with their head elevated about 90 degrees is the least appropriate action when a swimmer goes into shock because this position can impede proper blood flow and may exacerbate the condition. In cases of shock, especially when it is related to drowning or trauma, the swimmer needs to be laid flat and kept warm to optimize circulation and support the body in recovering from the shock.

In contrast, summoning emergency medical services is crucial since professional intervention is necessary to address the cause of shock and provide advanced medical care. Providing care until help arrives is also essential as immediate first aid can stabilize the swimmer’s condition. Monitoring breathing and pulse is vital to ensure the swimmer's vital signs are being tracked, allowing for timely interventions if their condition worsens. Each of these actions focuses on maintaining the swimmer's safety and wellbeing until professional help is available.