Janssen emerged from the water an hour later, dripping wet and slightly shivering but with a massive grin after sliding, slipping and bouncing all over the course.

Mrs Villas said it was the first time the family had swum in the lake and it would not be the last time. By the end of summer, it could prove to be a favourite attraction.

"I think I will have to come back next week with my friends," she said.

Molly Saunders and Jordan Thuma also spent an hour on the course on Saturday morning. The pair had booked well in advance, encouraged by recent warm days.

Ms Saunders said she had looked for the poor weather cancellation policy when she saw the cool forecast for Saturday, but was glad the pair had braved the conditions.

"It's like a playground for adults," she said.

She said the water temperature was "freezing" when she first got in, but it seemed to warm up by the end. "It's actually a beautiful day," she said.

"I think it was going to have to be pretty bad for us not to come out," Mr Thuma said.

"It's nice and bouncy, but it's much harder than I thought it would be. It's very slippery.

"Next time we come out, we might go around a few more times, I think."

After weeks setting up the inflatable course, the three business partners, who came up with the idea while on a fishing trip, finally got to see paying customers out on the water.

It was an exciting moment for a team that has heard its fair share of negativity.

Co-owner William Yeap said he had expected a split response to the new attraction, but had been pleasantly surprised by the enthusiasm.

"Less than two or three per cent of people dislike it. They're worried about water quality and so on," he told the Sunday Canberra Times as the first customers took in the park.

Mr Yeap encouraged people who were unsure or who perhaps had never taken a dip in the lake to try out the course.

"I just want them to come and try it. They'll see how fun it was," he said.

Mr Yeap said the team had been surprised by the support from the National Capital Authority, which had to grant approvals for the course. The project was more than a single-year investment, he said.

There had also been a strong take up in school bookings for the final weeks of term and more two-hour tickets were selling than one-hour sessions, Mr Yeap said.

ACT Liberal Senator Zed Seselja said in a statement on Friday that the new course would bring a new dimension to the lake, which would also soon see paddle boats return.

"As a passionate Canberran I am thrilled at the news of the additional activities that will be hosted on our magnificent lake," he said.

The Canberra Aqua Park will be open until March, with sessions limited to 100 people.