This is a fun activity. The gear doesn't cost much and is pretty simple. https://www.youtube.com/watch?v=R88sJMIPx14"]Rebecca 2 on the slack line - Muscle Beach, Santa Monica - YouTube
That looks hard. Is that just nylon webbing or something? I'm surprised I haven't seen that over here.
Line that is nylon and one inch wide is the most common and least expensive. There are fancier materials for the more advanced people who want to walk long lines or do tricks. It's tougher than it looks when you are first learning it, but it gets easier. Like ice skating or standup paddleboarding. Fun stuff.