The 22-year-old only just advanced out of the heats after touching home in 1:57.37minutes, good enough for 16th place overall and the final qualifying spot.
But having got his first swim in Barcelona out of the way, and with the 200m and 400m medleys to come, Pavoni claims it was a case of job well done.
"It gives me an extra swim to get me into the meet so I'll be back and I'll give it another shot," he said.
"It was OK, it was the best heat swim I've done some I'm happy I've got out and done my best time in the morning."
Ellie Faulkner declared herself pleased with the 2:00.56 she clocked in the heats of the 200m freestyle but it was only good enough for 25th overall as she missed out on the semi-finals.
Despite holding a personal best of 1:58.39, Faulkner insists preparations ahead of her favoured 800m freestyle, which gets underway on Friday, have been perfect.
"It was a good swim, it's the fastest I've gone overall for a heat swim in the morning so I'm pretty pleased with that," said Faulkner, who also fell in the heats of the 400m freestyle on Sunday.
"It's been good to get used to the atmosphere since Sunday and get used to everyone swimming, there have been some great swims up until now that I have been involved in."
Elsewhere, Ross Murdoch brought the curtain down on his first world Championships by also exiting in the heats.
His time of 28.00seconds was only good enough to put him 30th overall in the 50m breaststroke, having earlier in the meet made the semi-finals of the 100m.
Meanwhile, Dan Fogg, who came 38th in the 10km open water last Monday, had a disappointing start to his pool stint after failing to make it beyond the heats in the 800m freestyle.
- Sports & Recreation
- Ellie Faulkner