How long can a person survive underwater even after he's passed out?

Question

I mean, if he's passed out underwater and people eventually find him and revive him, let's say after 5 hours, will he just have brain damage and still be alive? like, a vegetable person?

Answer 1

Assuming the water is cold enough to cause hypothermia, hypothetically this person could survive about 6 hours because the body goes into a sort of stasis due to the cold.  However, if this body of water that he/she has fallen into is warm, the person will incur brain damage in about 6 minutes (about the same time that the heart will stop and breathing obviously ceases).  Hope this helps.  

Answer 2

If he's passed out underwater, he'll drown in less than a minute by breathing the water into his lungs. People continue to breathe even while passed out.

There would be no hope for survival regardless of the water temperature.