Which action is essential when caring for a swimmer with a suspected head, neck, or spinal injury?

Keeping the person's face out of the water is crucial when dealing with a suspected head, neck, or spinal injury. This action helps to ensure that the individual can breathe freely and avoid drowning while you are assessing their condition and waiting for emergency services to arrive. Maintaining an open airway is vital in these situations, as any movement could exacerbate potential injuries to the spinal cord or neck.

The other actions are not suitable in this scenario because they do not prioritize the swimmer's immediate safety and stability. Applying ice may not be advisable as there could be a risk of movement that could worsen the injury. Moving the swimmer to shallower water can also cause unnecessary shifting and risk further injury. Performing CPR is necessary only if the swimmer is unresponsive and not breathing, which is a specific scenario that wouldn't generally be the first step if there’s a suspicion of a spinal injury.