I have installed these on my 3UP. They are made specifically for the Spark, though, and I note you referred to a 'wave runner'? But I'll assume you're talking about about a Spark.
They attach by a 3M adhesive backing and a series of plastic 'darts'. You have to drill a series of 4mm holes for the darts, and then push the darts through. If you do it, be careful with the darts -- I accidentally crushed one of them and there are no spares in the kit. It's an official BRP kit, so it comes with instructions.
I have heard of one guy who found one of these bumpers came off in the water - I read that on another forum. However mine seem to be staying on, despite one of the panels being a dart short.
Before I got the bumpers, I was finding the sides of my Spark were particularly vulnerable around docks, and I had sustained a few scratches and nicks. However, installing these covered those up and I guess will protect it from future bumps and knocks.
How well do they protect? Hard to say because I haven't purposely tried to test them and find out. The rubber is quite thin, but I think they're better than nothing. I'm pleased with them so far, and I like the way they look as well.