The first time I came across one of these things was at a mall before I had ever heard about them. My first thought was 'how much air are in those things' and 'what happen if the person gets stuck in the center of the shallow pool'. I think it would make sense to have a way for the person to escape from the inside by themselves in case of an emergency, but the worse case scenario seemed to be that one of the workers would have to get there legs wet to retrieve the ball. There may be a scenario in which real danger could arise, but other past times like bungee jumping and sky diving seem much more dangerous. Even playing football or hockey seem like games your are more likely to be injure doing.
Video embedded below.