When those first came-out they were marketed on TV and the web. I looked into them and there were numerous leaks and blow-outs.

I'd still be very careful with a marina or other robust pressured water line. Further, I would make sure that you shut-off the washdown valve (and pump, for that matter) if it's in a locker on the boat. If one of these hoses develop and aneurysm or bursts, you'd be sorry.