For three years running, Magnussen was considered the fastest freestyle swimmer in the world and he made a visit to Cobargo as part of a swimming clinic road show.

Magnussen was warm and charming with the kids, who left the clinic inspired and exhausted after almost three hours of extensive training.

The former Olympian opened the session sharing some of his back story about the immense dedication it took to become a world-class swimmer, detailing the heartbreak of competing at nationals only to find himself outside the top 50.

He said how he had grown up in Port Macquarie and had been inspired by a visit from an Olympian himself.

"When I was a kid, we only got the chance to have a visit from one Olympian, when I was about 15 I got the chance to race Libby Trickett and I won," Magnussen said, beaming before issuing an open challenge to the Cobargo swimmers.

"That was probably a career highlight for me and I want to give you guys the same chance I had, so when we finish today if anyone wants to race me - if you win, I'll give you all my medals ... and my car."

Plenty took him up on the offer and a few outstretched hands came close, but the now-retired swimmer still showed remarkable speed, demonstrating one fast lap where he was clocked at a little over 10 seconds across the 25-metre pool.

Club president Beck Grenfell said the day was an incredible success.

"It totally surpassed our expectations," she said. "It was priceless for the kids and an unforgettable experience."

"We knew there was a lot of potential for it to be good for the kids, but it was just amazing."

Ms Grenfell said she had concerns some of the younger swimmers might have got distracted or lost interest, but said Magnussen captivated the crowd.

"He had the kids in his pocket from the second he started talking, he won them over and it was amazing," she said.

The large group of kids were shown specific stretches and exercises to both increase their flexibility, but also boost their core strength, which Magnussen said was critical for Freestyle, but also improving any swim technique on the whole.

The group were then shown several techniques in the pool from form, posture to turns and even diving.

"We were all able to get something out of it," Ms Grenfell said. "You would be silly not to take on what he was teaching "

The club have already begun implementing the warm ups, stretches and techniques with Monday morning squad swimmers refreshing the lessons.

Ms Grenfell also thanked life member Barry Benny who donated $1000 towards the cost of the clinic.