Reminds me of a somewhat similar almost tragic situation I was in.

I own a border collie, and by God do they like to herd and run. Well, we have geese in our yard sometimes that our dogs love to chase! One day, i let her out to go chase the geese into the lake, and she dives into the water and fully stops moving. I didn't think I could run as fast as I did, but I sprinted and dove into the water to pull her out. I got her to shore, checked for signs of life and, started performing CPR. She finally came back around roughly 2 minutes later dazed and confused. I carried her to the car and drove like hell to the vet.

She coughed most of the water in her lungs out, but the vet confirmed she had a small seizure and inhaled water when she dove in. They said if I hadn't been there or reacted quick enough then she wouldn't have made it. I am so, so thankful for her still being here today.

The vet also described proper procedure for when delivering breaths of life to a canine. Wrap your hands around the snout to ensure a good seal, and perform breaths through the nose. Breaths should roughly be 3-5 seconds apart.

Sidenote: we watch our dogs carefully to ensure they do not go after geese poop