If you were attempting a water rescue of two children and you retrieved one, but he wasn't breathing, do you go back for the second and then attempt CPR on the first or stick with the first child and start CPR?

If a canoe overturned and dumped two kids into the water and neither could swim and both went under, and you were nearby, how do you decide on the rescue mission? Once they go under you’ve got roughly four minutes to get to both of them. If you get one secured, but he isn’t breathing do you go for the second child or stay with the first? Or do you work on the first one and let the other one possibly perish? You’re good in the water, so it isn’t a question about you. How do you decide?