The Aucklander had qualified fifth fastest from the morning's heats and seemed set fair to make the top eight for tomorrow's final.
He had the quickest swimmer from the morning heats, Australian Christian Sprenger, alongside him in the second semifinal.
However Snyders had a bad start, and although he recovered to sit on Sprenger's shoulder in second when they turned for home, he faded to finish seventh in 1min .15s. That left him 15th overall.
"I'm pretty disappointed," Snyders said after the race.
"I gave it everything but it just didn't come tonight."
"The wonky start meant he lost momentum and although he knew he was right in the frame at halfway, "it wasn't as smooth as I'd have liked. Even in the last 20m I could feel myself fading".
What made it more depressing for Snyders was he'd set a national record in the heat, in winning that race in 59.78s.
To demonstrate the strength of the field, that time would have had him equal eighth fastest qualifier for the final alongside American Brendan Hansen.
Sprenger won the semifinal in 59.61s but he was left trailing the first three finishers from the opening semifinal, which was won in an Olympic Games record time of 58.83s by South African Cameron van der Burgh, with Italian Fabio Scozzoli and Australian Brenton (crrt) Rickard the next quickest.
The fastest 11 in the semifinals all clocked under one minute. Snyders said he couldn't be too unhappy, given the record in the morning and the quality of the field.
''I went in believing in myself, and 60.1s is not that slow. But it just didn't feel like it was connected tonight," he said.
Snyders now turns his attention to the 200m breaststroke on Tuesday.
The opening finals night of the meet had the first world record of the Games, through Chinese swimmer Ye Shiwen, who absolutely flew home over the freestyle leg in the women's 400m individual medley to touch in 4:28.43, fully 2.84s ahead of American Elizabeth Biesel who had the best time of the year before the race.
Former world recordholder and Olympic champion Stephanie Rice finished sixth.
And American Michael Phelps, hoping for three more medals at these Games to become the most-medalled Olympic athlete, was squeezed into fourth in his first event, the 400m individual medley.
Team mate Ryan Lochte turned in a sizzling swim to win in 4:05.18, ahead of Brazilian Thiago Pereira and Japan's slick 17-year-old Kosuke Hagino.
Phelps has 16 Olympic medals, two behind Russian gymnast Larissa Latynina, from the 1956-64 Games.
There was also two Olympic records in the session. Another Chinese swimmer, Sun Yang, recorded 3:40.14 in winning the 400m freestyle, clipping .45s off Australian Ian Thorpe's old mark.
And Australia's 4 x 100m freestyle quartet of Alicia Coutt, Cate Campbell, Brittany Elmslie and Melanie Schlanger combined to produce 3:33.15, beating home the Dutch foursome by .63s, and taking .61 off that nation's old Olympic record from four years ago.
- David Leggat, NZ Herald
