Dog Drowning

The first thing to do is remove the drowning dog from the water and put it on its side on a firm surface with your dog's head a little lower than the rest of its body so that the water come out of its lungs. Begin artificial respiration (AR or mouth to mouth) if your dog is not breathing and if it has no pulse then begin CPR (cardio-pulmonary resuscitation). After your dog has recovered dry it off and move it to a quiet spot so it can rest. Keep your dog warm (watch for overheating or shock) and check for any other problems or injuries. Dirty water can cause infections and salt water can cause poisoning so be sure to let your dog's veterinarian know what kind of water the dog was in.  Seek immediate medical attention.

Dog Frostbite

Frostbite is the result of the blood vessels freezing, which then stops the tissue from receiving the oxygen and nutrients that it needs which can lead to gangrene. With severe frostbite the circulation cannot be restored and so the affected area shrivels and dry gangrene set in (without any inflammation).
When the frostbite is less severe and the body tissue was not too damaged it is possible for there to be complete recovery.  However even in these cases it is still possible for the tissue to become horribly inflamed and gangrene can result. When there are obvious signs of freezing but the skin can still move frostbite is not too serious. But if the skin is frozen solid this indicates that the frostbite is very severe. Give your dog hot water, tea or coffee to drink but not any form of alcohol. Bathe the affected tissue warm water. Do not apply hot water, ice, oil, dry heat to the frostbitten area and do not try and restore the circulation by massaging the affected tissue as these things will only cause the affected tissue to become more severely damaged. After the frostbitten area has defrosted dry it off gently and carefully, and then let your dog rest. Keep it warm but do not use a heater. Keep vigil over your dog for signs of shock or other complications. Seek immediate medical attention.