Pond safety cover recommendations (with added duckweed...)

I think I see what you're saying, but my reading of the sites was different - they both seemed to show a reasonable mix of installations both over and under the water. They don't seem to hide the fact the above-water installations are possible or that they are safer. I'm also suprised that DiamonDeck installations in schools would get OFSTED approval if they didn't meet RoSPA guidelines.

The more I think about it the more I think this isn't the best way forward for us regardless (having the cover in small pieces is still going to make it a lot of hassle to try and skim duckweed, and the fewer pieces there are the safer it instinctively feels), I just like to understand things :o