About 3.5 seconds. I'm pitiful...

For myself, it's about 90 seconds. However, check out Guillaume Nery. Almost 8 minutes, and free dives to 120 METERS! His video of "BASE jumping" into deans blue hole is amazing!

Infinity... see below.

Here is a great trick to play on people next time your in the hot tub. Go under and cover one of the air jets with your mouth. The air will displace the water and you can slowly breathe as long as you want. Do it for a minute, then two. After others are suitably impressed, stay down until someone prods you. Go limp until they pull you out. Bonus points if you can make it until the CPR starts. Seems cruel to do but with the right friends it comes off fairly well.

Myself, unassisted? Guessing 40-50 seconds.

Note that the body responds with oxygen conservation when diving. Quite rapidly. Heart rates under 50 even when moving. This is how you stay down 2 min - thanks to mother nature ...

Heart rate in humans during underwater swimming with and without breath-hold. - PubMed - NCBI

G

My answer: Same amount of time as above water..........

2:45 while sitting on the couch last week. Have not tried underwater in a while. Supposedly, you can hold it longer underwater than above.

I'm 55 and still freedive spearfish often in the kelp around Socal beaches and the Channel Islands. I just timed myself and can only hold my breath 1:45.

Spearfishing around here you don't need to hold your breath very long unless you make a bad shot and your fish swims deep into the rocks or the spear line wraps around kelp stalks. Most of the white sea bass, Halibut, and yellowtail I spear are less than 20' down.

I used to do open ocean on floating kelp paddys…Until a 200-300lbs Mako came up and bumped me at the 209 Bank. He followed me all the way back to the transom platform. That was enough for me. I lost my nerve and only do shallow water stuff now.

Sorry, I could not resist...
https://youtu.be/R7boUa5FXBg?t=35s

I can do 3 laps underwater in a normal 40 foot pool without coming up for air. Have no idea how long that is, but I know the last lap feels like an eternity.
It has gotten better since I quit smoking

Pretty good !!! Dunno above under/above water.... Admittedly it depends on what you do under water... Also pressure must play a part... While I got about 3 min back in the day not moving in a pool, I'd only get 1 minute exerting myself dropping to the bottom, swimming, picking up sea food or whatever.... I don't think everybody has the same degree of metabolic slowdown / conservation either. Those pro free divers that go 300ft down are crazy calm, they're practically whales... I've seem a documentary where the blood flow centers on core organs only, but with them to a much higher degree than the average street person.... Genetics I guess... It's a crazy sport !

I also grew up in SoCal and body surfed a couple times a week for years (and nary a nibble from mean old Mr. Shark).

Back in the day I could do a lap underwater of a regular pool... today? Not so much. :(

When I was in HS, I ran track. As a training technique I tried to hold my breath for 10 - 15 seconds every 3rd breath while jogging. I'm not sure if it was that of the fact that I was running a lot but I shaved 45 seconds off my mile that summer to come close to a 5 min mile as a Sophmore. I later switched to sprints for my Jr and Sr year. I used that technique thinking about how good swimming is due to resistance and breath management coupled with anaerobic activity. I'm sure I suffered brain damage...

I keep reading the title to this and thinking

The rest of my life.

Non twisted answer...
About 45 seconds before I choose to come up for air

I was gonna call bull**** on that until I googled that the record is 22 minutes... And he's a scientologist, for pete's sake ;-)

I can do just under 2 minutes, or at least I could in November before my last speardiving trip.

I'm reading a great book about freediving right now called Deep, would highly recommend: http://www.amazon.com/dp/B00E78ICX8/

Do you still do freediving now Craig?

Okay, Vash, fess up!

Me, 30 seconds tops.

RE: Bodysurfing... when the waves are big... holding your breath is not optional, great incentive to hold your breath when the ocean has you pined to the bottom. ;)

Depends. With or without asthma inhaler? :)

In our backyard pool my dad did 3 minutes on the bottom. But only because mom lost her footing.

2.5 seconds now.