As a teenager who swam I could hold it over two minutes. Now, as an old man with a lifetime of wear and damage, barely over 30 seconds.
As a boy my town had 4th of July events. One was an underwater swim in the municipal pool. It was a 25 yard pool. At 10 years old I swam three lengths underwater. Most surfaced at a length or less, a few made the turn, none made the second turn other than me, but wanting to show off I did the third length anyhow. I won a goldfish. It died before I got it home.