The organisation's executive director, Craig Johns, has warned the sport's summer events calendar could be cut in half and membership severely diminished if the aquatic attraction earmarked for Black Mountain Peninsula was allowed to go ahead.

The National Capital Authority last week started public consultation on a local group's plans to install and operate the adventure park from November to April 2020.

The inflatable obstacle course would include tunnels, bridges, slides and swings. Food trucks would also be parked on the peninsula, according to plans presented to the authority and the ACT government.

The privately funded operation was expected to cost about $250,000.

Mr Johns said the proposed aqua park would be a "fantastic addition" to Lake Burley Griffin, so long as it was not based off Black Mountain Peninsula.

He said the aqua park's proposed location and months of operation would make it impossible to host triathlon events at Black Mountain, which has been a home for the sport for more than 30 years.

Triathlon ACT hosts two of its four annual events off the peninsula. Larger triathlon races are held at Rond Terrace.

The Australian mixed-team triathlon championships are scheduled to be held at Black Mountain in January next year, although that event could be in jeopardy if the aqua park gets the green light.

Mr Johns said those were the only two locations available to regularly host triathlon races on Lake Burley Griffin.

Locations which have previously hosted events, such as New Acton and Yarralumla, are now deemed unsuitable for various reasons, including the cost of road closures and the effect on local residents.

He said the loss of Black Mountain as an event venue would be "catastrophic" for Triathlon ACT, which has experienced a 66 per cent increase in membership in the past four years.

"It is also significant for the next generation because this is really the only appropriate place for young swimmers," he said.

Mr Johns nominated a range of locations on Lake Burley Griffin which he considered more suitable for an aqua park, including Weston Park, West Basin, Attunga Bay and the area adjacent to the YMCA Canberra Sailing Club.

The group behind the attraction, Canberra Aqua Park, specifically chose the Black Mountain location because of its relatively high water quality.

Water monitoring data included in its application to the authority showed the Black Mountain section had been closed on average two weeks a year since 2011-12. That compared to about seven weeks a year at Weston Park, which was the other location under consideration.

A National Capital Authority spokeswoman said it had met with Triathlon ACT representatives to discuss the sporting body's concerns.

The spokeswoman said the authority would consider all feedback received during the public consultation period, which ends on June 3.