Sorry, this may be a blindly stupid question but the inference from the norms is that any of these measures is independent of the others. Thus for example if you have an alarm, then you don't need a fence. I had been given to believe that you had to have a physical barrier to provide passive protection. How does a cover help in this regard as it has to be removed in order to use the pool? Equally, if you protect your pool by an alarm, what measures do have to put in place to respond to the alarm? Given the lack of bystander response to house or car alarms, a pool alarm isn't going to help much. Like many people, I have a pool that is the wrong shape to easily fit an abri or sliding cover and it is very close to the house, which means a fence will divide the patio in two. All help gratefully received.