WATCH: Daredevil Takes Free Solo Slacklining Sport to New Lengths

He crossed a 210-foot-long rope between 2 cliffs sans a harness or safety net.

— -- Spencer Seabrooke recently had the free solo slacklining experience he'd been looking forward to since he started the sport more than three years ago.

He said today that the length of the slackline had set a new record.

"It felt amazing," Seabrooke, of Vancouver, told ABC News today. "It's an accomplishment that I've been dreaming about a long time. ... It was the biggest free solo walk I've ever done."

Today, he said he couldn't remember what music had helped get him over the slackline.

"It was some kind of ambiance that my friend put on my MP3 player, but it was doing the trick," Seabrooke said.

Slacklining is similar to tightrope walking but the slackline is made of a wide, nylon webbing that allows it to sag and sway under the walker. The sport is usually practiced just a foot off the ground, Seabrook said, with a slackline tied between two trees.

When the sport is held hundreds of feet in the air, it's considered "highlining." And when highlining is done without a harness or safety net, it's called "free soloing."

Seabrooke said he wore a harness when highlining "98 percent" of the time but said he considered free soloing the "pure way" of slacklining.

"You take the harness off and do what you've done before. ... It's really high in the air. You can definitely, like, feel that exposure underneath you," he said. "It's just a mental game that you're playing with yourself."

During the week, Seabrooke pours concrete for homes -- "You gotta pay the bills, so," he said -- and on the weekends, he slacklines.

"I've been looking at doing this for a really long time," he said. "I've just been waiting until I was ready. ... Aug. 2 was the day, I guess."

Next up for Seabrooke: BASE-jumping and skydiving in September.

ABC News' Jenn Metz contributed to this report.