Daredevils pulled off a jaw-dropping stunt over the Stanley Park seawall Tuesday, but the Vancouver Park Board wasn’t impressed.

The thrill-seekers were filmed straddling a slackline that stretched from a cliff out to Siwash Rock, a 32-million-year-old outcropping near the Lions Gate Bridge that has cultural significance to local First Nations.

It caught the attention of passersby, but Park Board general manager Malcolm Bromley cautioned against encouraging such stunts.

“When it crosses a line and endangers public safety or really disrespects an important cultural place like Siwash Rock, that really raises a lot of concerns for me,” Bromley said.

There’s a clearly marked no trespassing sign metres from Siwash Rock, and Bromley said the group of slackliners clearly violated Vancouver bylaws.

Adam Mertens, who took part in the spectacle, defended their actions Wednesday and insisted no damage was done to the landmark.

“We weren’t putting any metal into the rock, we weren’t changing the actual structure at all,” Mertens said.

He also disputed that anyone involved in the high-flying stunt or on the seawall below was ever put in harm’s way. The group is well-experienced, having slacklined at the Chief in Squamish, and they wear safety gear to prevent them from falling all the way to the ground.

“I wouldn’t encourage anyone to do the same thing we’ve done, but we did it with a certain skill set,” Mertens said.

The Park Board said it’s still deciding whether to fine the daredevils, who have promised not to slackline at Siwash Rock again.

With a report from CTV Vancouver’s Scott Robert