I think it depends on your age, the temperature of the environments, etc. I know of a teenager who was rescued from drowning after 15 minutes (estimated). She revived and was undamaged.
There is really no way to know, since everyone is different and I would guess 99.9% of the time a person would not even survive going that long without oxygen. If the person's body was really, really cold while they were not breathing, that can help prolong brain damage for a little while, but even then there is no guarantee.