If you adopt a blank canvas approach it's just so simple to see the tremendous benefits of this unique bed over every other sleeping surface. A famous Scotsman once said 'Ye canna change the laws of physics' and it really does come down to that. Consider every other bed, be it memory foam, a sprung bed, a feather bed, futons or whatever - all of them depend on you compressing the sleeping surface, squashing down the foam/springs etc. The support you get is dependent upon your weight and at that, the surface is only touching you, not raising itself up to meet your body.
A waterbed however, works by displacement – the old Archimedes principle whereby you press down in one place and the water goes up elsewhere, and it literally does go UP, up into the small of your back, up into the nape of your neck, even up under your knees. So whatever shape, weight and size you are, the water cannot help do anything but support your entire body from tip to toe. Common sense really. Beat that NASA!