I'm a master's swimmer, but I'm only really now picking up pace after having to take a couple of years off to properly build strength in my shoulders to carry on after a rotator cuff injury.
Around May 2016 I decided to try jumping back into the squad training after just under a year of rehab. It was my first session back; I was massively unfit. At the end of the session the coach got us to do a 100m race. I was up against a couple of guys who'd been faster than me in the session and was determined to show I hadn't slipped that much. I ended up swimming a 1:07 for the 100m free beating one of the faster guys. I couldn't believe the time. I don't really know what happened, but I REALLY wanted to win this race and just went for it. A few weeks after this my shoulder wasn't holding up to the training volume and I had to drop back into more gym rehab type stuff.
I finally got back into the pool properly around May of last year. The best time I've swum in a similar scenario since has been a 1:07 and I'm the fittest and strongest I've been for years.