I was an in-water rescue specialist for a SAR organization when I was younger. I was the one who trained for jumping into the water and retrieving people, performing CPR and any necessary first aid while I was there. Swim through surf onto rocky shorelines to get trapped and / or injured folks to safety etc.
One of the first things that got drilled into us on the medic side was that CPR almost never results in the person coming around like on TV. Your job is simply to keep oxygenated blood circulating until the medical attention needed to revive them is available.
I would have been astounded if you reported pulling an unconscious and non-breathing person out of the surf and had them come to on the beach.
If it's any consolation, there really isn't anything you can do to fuck up in that situation short of doing nothing.