I think this would vary from person to person. And also it can increase with training. A few years back, I used to go swimming a lot and I could hold my breath for about two minutes thirty seconds tops. To do it, I'd close my eyes and relax under water. Relaxing my muscles meant less oxygen was consumed. But now I can only hold my breath for thirty seconds or so.

Then for some people, they are able to hold their breath for strange reasons. Once, on Discovery channel, a man claimed to able to hold his breath for ten minutes. He went with a boat to the middle of a lake and they dropped an anchor. The man wore a body can and jumped into the lake, held the rope and swam down to the anchor.

He stayed there for ten whole minutes.

The body can showed that he didn't use an oxygen tank while down there so when he got back up, they ran some tests. It was discovered that the man's body switches from aerobic respiration to anaerobic respiration when deprived oxygen. This means that he can survive for a while without oxygen.